Search found 100 matches

by Vince Li 2A
Sun Mar 07, 2021 9:45 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: k'
Replies: 4
Views: 23

Re: k'

The difference is that k' is a pseudo rate constant, while k is the actual rate constant. Assume a reaction A + B + C ------> Products. Let's say you want to find the order of A individually, but because there are three reactants total, it makes the calculations complicated. To resolve this, you hav...
by Vince Li 2A
Sun Mar 07, 2021 9:35 am
Forum: First Order Reactions
Topic: How to determine the Order of reactions
Replies: 8
Views: 32

Re: How to determine the Order of reactions

It should be carefully noted that the order of reactions is different from the order of the reactants and products. In order to determine the order of the reaction, you must determine the order of the reactants/products. To do that, you must have experimental data given in the form of initial concen...
by Vince Li 2A
Sun Mar 07, 2021 9:29 am
Forum: General Rate Laws
Topic: Derivation of integrated rate laws and half-life equations
Replies: 7
Views: 20

Re: Derivation of integrated rate laws and half-life equations

No, I am sure that the derivations are put in place to understand where the equations come from. Overall, knowing where the equations come from allows for a greater understanding of the calculations and chemistry behind it, instead of just memorizing equations.
by Vince Li 2A
Sun Mar 07, 2021 9:28 am
Forum: General Rate Laws
Topic: Week 9/10 Sapling #3
Replies: 5
Views: 18

Re: Week 9/10 Sapling #3

I like to think of calculating instantaneous rate as finding the slope of the tangent line at that point. What other way could you get the slope of that tangent line? You could find the secant line that has the same slope. In other words, a time at 0 seconds and a time at 80 seconds will average out...
by Vince Li 2A
Sun Mar 07, 2021 9:22 am
Forum: General Rate Laws
Topic: Order of a reaction
Replies: 4
Views: 18

Re: Order of a reaction

The order for each reactant/product is typically obtained through experiments. Looking at a table which contains the initial concentrations of the reactants/products, and the initial rates, you are able to determine the order of the reactants/products. Remember the general rate law equation, which i...
by Vince Li 2A
Mon Mar 01, 2021 11:19 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: -d[R]/dT versus d[P]/dt
Replies: 12
Views: 49

Re: -d[R]/dT versus d[P]/dt

The two will equal each other only if in the balanced equation, the stoichiometric coefficients are the same. If not, then you have to refer to the Unique Instantaneous Rate law equation.
by Vince Li 2A
Mon Mar 01, 2021 11:01 pm
Forum: General Rate Laws
Topic: Unique Rate Equation
Replies: 5
Views: 32

Re: Unique Rate Equation

I think it's better if you work from the beginning, and then the fractions will make sense. Using the example from the lecture, looking at the chemical equation for 2NO2 to 2NO + O2, the rates of the NO2 disappearing is two times the rate of O2 forming, with a relationship of 2 to 1. In other words,...
by Vince Li 2A
Mon Mar 01, 2021 10:57 pm
Forum: General Rate Laws
Topic: Unique Rates
Replies: 6
Views: 24

Re: Unique Rates

Unique rates is a fancy relationship for determining the rates of reactants disappearing and the rates of products forming by setting them equal to each other in an equation. Note how you can either have unique instantaneous rates or unique average rates.
by Vince Li 2A
Mon Mar 01, 2021 10:55 pm
Forum: General Rate Laws
Topic: Mechanism of a Reaction
Replies: 6
Views: 19

Re: Mechanism of a Reaction

A mechanism of a reaction involves the step by step processes that go from a reactant to a product. A reaction can have multiple reactions in-between the overarching reaction (think of it like Hess's Law), and each reaction can either go fast or slow. Determining which rate of the reaction dominates...
by Vince Li 2A
Sun Feb 28, 2021 6:41 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Calculating equilibrium constant
Replies: 11
Views: 28

Re: Calculating equilibrium constant

The standard values are given as reductions, so you have to flip the sign in order to give the standard value for oxidation.
by Vince Li 2A
Sun Feb 28, 2021 6:29 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: E naught Cell equation
Replies: 9
Views: 23

Re: E naught Cell equation

Yes, it is always cathode minus anode. Keep in mind that the subtraction is only to account for the fact that the standard reduction values are different. If you converted the standard reduction value for the anode into a standard oxidation value (if it even exists), you add the values.
by Vince Li 2A
Sun Feb 28, 2021 6:26 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: E naught = 0
Replies: 13
Views: 47

Re: E naught = 0

For concentration cells, it is essentially the same compound or species on either cell. Thinking back to standard conditions, if both of the cells are the same thing, then there is no voltage difference between them, because they are the same. As a result, the E naught is 0.
by Vince Li 2A
Sun Feb 28, 2021 6:16 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: E vs E naught
Replies: 30
Views: 60

Re: E vs E naught

E is not under standard conditions, E naught is. Standard conditions are at 1 atm, 1 mols of each solution, and at 25 degrees Celsius. Note that when calculating K in one of the equations, E is equal to 0, not E naught.
by Vince Li 2A
Sun Feb 28, 2021 6:13 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Moles in ΔG = -nFE
Replies: 42
Views: 86

Re: Moles in ΔG = -nFE

For me, I would always be confused with change in moles. However, there is a difference between that and moles of electrons transferred. In this case, you use moles of electrons transferred.
by Vince Li 2A
Sun Feb 28, 2021 6:11 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: anode vs. cathode
Replies: 12
Views: 29

Re: anode vs. cathode

To be honest, all that really matters is understanding which species is being reduced and which species is being oxidized. I feel like the idea of a left or right is very arbitrary. Typically though, the anode (oxidized) is on the left, while the cathode (reduced) is on the right.
by Vince Li 2A
Sun Feb 21, 2021 4:02 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Q and K
Replies: 36
Views: 87

Re: Q and K

Q is the same thing as K, except in Q, the reaction has not finished. Let's say that the equilibrium constant (K) for a reaction is 2. If the Q is calculated to be 0.5, in order to reach K, the numerator has to be larger. In terms of the reaction, more products need to be formed to increase the nume...
by Vince Li 2A
Sun Feb 21, 2021 4:00 pm
Forum: Calculating Work of Expansion
Topic: Textbook Question 4A11
Replies: 3
Views: 18

Re: Textbook Question 4A11

There is a difference between specific heat capacity and heat capacity. Heat capacity is an extensive property, meaning it depends on how much material there is. Specific heat capacity is an intensive property, in that the value is not affected by how much material there is. In this case, calculatin...
by Vince Li 2A
Sun Feb 21, 2021 3:54 pm
Forum: Calculating Work of Expansion
Topic: Irreversible vs. Reversible
Replies: 6
Views: 43

Re: Irreversible vs. Reversible

A reversible reaction is when the external and internal pressure are equal, so the work of expansion happens in small increments. As a result, the pressure changes slowly in that long time period as the reaction is going. In an irreversible reaction, because the external pressure is so much higher/l...
by Vince Li 2A
Sun Feb 21, 2021 3:52 pm
Forum: Calculating Work of Expansion
Topic: Value of Q
Replies: 20
Views: 47

Re: Value of Q

Q is the same thing as K, only that the reaction has not reached equilibrium. The problem should give the values of the concentrations for the products and reactants, so you can calculate Q knowing the balanced equation. Depending on the value of Q, the value of the Gibbs free energy will determine ...
by Vince Li 2A
Sun Feb 21, 2021 3:49 pm
Forum: Van't Hoff Equation
Topic: Van't Hoff equation
Replies: 10
Views: 46

Re: Van't Hoff equation

The Van't Hoff equation allows you to calculate K at a different temperature, given the initial temperature and initial K and the final temperature. The other equation provided only helps you calculate the K, given that you know the final temperature, and the Gibbs free energy. Comparing the two, th...
by Vince Li 2A
Sun Feb 14, 2021 4:11 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Adding Equations
Replies: 16
Views: 42

Re: Adding Equations

Yes, because standard enthalpies or standard entropies are both state functions. Keep in mind it applies to enthalpies and entropies in general.
by Vince Li 2A
Sun Feb 14, 2021 4:09 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Sapling Week 5/6 HW 18
Replies: 11
Views: 91

Re: Sapling Week 5/6 HW 18

You add the standard Gibbs free energies of the products and subtract them by the reactants. Keep in mind that you have to multiply this by 1000 to obtain it in joules. Take that number, divide it by -RT to obtain the equation ln(K) = number. Use e ^ number to obtain the K value.
by Vince Li 2A
Sun Feb 14, 2021 4:05 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Sapling 15 week 5/6
Replies: 6
Views: 40

Re: Sapling 15 week 5/6

Flip the second reaction and multiply by 2. This causes the standard enthalpy of the reaction and the entropy of the reaction to be multiplied by -1, and then doubled. Add the two reactions to obtain the final reaction. Keep in mind that you have to change the standard entropy to kJ before you find ...
by Vince Li 2A
Sun Feb 14, 2021 4:02 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Sapling Question #16
Replies: 8
Views: 45

Re: Sapling Question #16

Believe it or not, no temperature is involved. Because it is asking for the standard change in Gibbs free energy, you treat this problem the same as a standard change in enthalpy. All you do is add the Gibbs free energies of the products and subtract it with the standard Gibbs free energies of the r...
by Vince Li 2A
Sat Feb 06, 2021 11:52 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Difference in volume and temperature
Replies: 6
Views: 199

Re: Difference in volume and temperature

I agree with Andrew, it depends on the context of the system. If it is a reversible expansion, you will likely have to use the equation for the isothermal reversible expansion of an ideal gas, which involves volume. If it is not a reversible expansion, I would assume you have to use the other equati...
by Vince Li 2A
Sat Feb 06, 2021 11:46 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Heat vs Thermal Energy
Replies: 7
Views: 21

Re: Heat vs Thermal Energy

Yeah, I just searched this up and Lily is right. Thermal energy is the energy inside a system that is not moving or being transferred anywhere. Heat is thermal energy actually being transferred to another region. I don't really know why someone decided to make two terms like this, but I guess it mak...
by Vince Li 2A
Sat Feb 06, 2021 11:43 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: How to identify Thermodynamic
Replies: 3
Views: 37

Re: How to identify Thermodynamic

You can only have an isothermic system that is reversible, I believe. That would make sense, because in an irreversible reaction, the system is unable to maintain a constant temperature, due to the sudden change in internal energy of the system. Remember how because a reversible takes a long period ...
by Vince Li 2A
Sat Feb 06, 2021 11:40 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: isothermal reactions
Replies: 9
Views: 38

Re: isothermal reactions

I think the basis of isothermal reactions is that the temperature remains constant. All of other factors, pressure and volume, are dependent on the fact that temperature is constant. In its essence, the temperature remaining constant, due to how the energy being converted to work is immediately bein...
by Vince Li 2A
Tue Feb 02, 2021 9:43 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: delta U versus delta H
Replies: 5
Views: 17

Re: delta U versus delta H

Delta U is the same thing as delta H, only if the pressure of the system remains constant. I guess you could say that delta H is a type of delta U. U represents internal energy, and H represents enthalpy, which is a type of internal energy under the certain condition.
by Vince Li 2A
Tue Feb 02, 2021 9:40 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: External force
Replies: 6
Views: 179

Re: External force

I think there are external forces in both types of reactions, irreversible and reversible. As long as you have an external pressure that is countering the force of the internal pressure, you will have an external force. In both reactions, suppose you established that the system has exerts 2 atm insi...
by Vince Li 2A
Tue Feb 02, 2021 9:37 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: External Pressure
Replies: 32
Views: 63

Re: External Pressure

I think that external pressure depends on what you label as the system. Typically in the lecture, Dr. Lavelle established that the system was inside the beaker itself, and that the external pressure was the atmospheric pressure outside of the beaker, typically 1 atm. However, suppose that the system...
by Vince Li 2A
Sun Jan 31, 2021 10:13 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy vs heat
Replies: 20
Views: 88

Re: Enthalpy vs heat

Enthalpy is a type of heat. The most important distinction is that enthalpy is when heat is transferred from the system to the surroundings or vice versa, at a constant pressure.
by Vince Li 2A
Sun Jan 31, 2021 10:11 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: System and Surrounding
Replies: 4
Views: 26

Re: System and Surrounding

Those are two different contexts. The first relationship is to show that in an endothermic and exothermic reaction, the heat produced by a system is equal to the heat transferred to the surroundings. The second relationship is just to communicate that the surroundings will always be larger than the ...
by Vince Li 2A
Sun Jan 31, 2021 10:01 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Ways of Changing the Energy in the System
Replies: 5
Views: 29

Re: Ways of Changing the Energy in the System

Work is a form of energy that is not a state property. If the system is expanding by either/and producing heat from an exothermic reaction or producing moles of gas, then the system is doing work of expansion, in that the system is pushing at some external pressure. In this case, the volume is incre...
by Vince Li 2A
Sun Jan 31, 2021 9:46 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Closed Thermodynamic System
Replies: 4
Views: 17

Re: Closed Thermodynamic System

Yes, a closed system means that actual matter cannot leave the system. In the scenario, it means that water vapor can not leave the beaker, due to the lid on top to keep the system sealed. However, the heat generated from the system, which is exothermic, is why the system is able to transfer energy ...
by Vince Li 2A
Sun Jan 24, 2021 12:52 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy (ΔH) vs heat (q)
Replies: 3
Views: 35

Re: Enthalpy (ΔH) vs heat (q)

I think the main distinction is that enthalpy is the amount of heat transferred at a constant pressure. While heat can be transferred as well, either in a constant pressure environment, it can also not be. In this case, heat would not be a state property, because it wouldn't be enthalpy. For example...
by Vince Li 2A
Wed Jan 20, 2021 10:54 am
Forum: Identifying Acidic & Basic Salts
Topic: How to identify acids and bases?
Replies: 7
Views: 57

Re: How to identify acids and bases?

An acid is a compound that either gives off a H+ proton (Bronsted Acid) or is an electron pair acceptor (Lewis Acid), due to how the H+ ion leaves to form a coordinate covalent bond with the base, and the original bond becomes a lone pair on the acid. A base is a compound that accepts a H+ proton (B...
by Vince Li 2A
Wed Jan 20, 2021 10:48 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Autoprotolysis
Replies: 6
Views: 36

Re: Autoprotolysis

Autoprolysis can only occur between two identical molecules that are amphiprotic/amphoteric, meaning acting as an acid or a base, depending on the system's environment. Another example can be ammonia, due to how two identical molecules of ammonia can act as an acid and a base.
by Vince Li 2A
Wed Jan 20, 2021 10:42 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH for Strong Acids
Replies: 3
Views: 32

Re: pH for Strong Acids

You would assume that the strong acids completely dissociate, because these acids are more readily able to give off a proton, and that the anion is more stable afterwards. As a result, you would just use the concentration of the strong acid/base to calculate the pH or pOH. Also, make sure to look at...
by Vince Li 2A
Wed Jan 20, 2021 10:39 am
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Polyprotic Acids
Replies: 2
Views: 23

Re: Polyprotic Acids

Polyprotic acids have extra protons that they are able to give off. Various polyprotic acids can either be strong or weak, but in order to calculate the total Ka, you have to multiply together the various Ka values from each of the equations parts to obtain the total Ka.
by Vince Li 2A
Sat Jan 16, 2021 11:54 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Acid and Bases always Happening in Water?
Replies: 3
Views: 35

Re: Acid and Bases always Happening in Water?

I would assume that Acid and Base always and only happen in water, because of the presence of the H+ ion, which we would classify that as H3O+. We wouldn't have a hydronium ion if the reaction didn't have water involved.
by Vince Li 2A
Sat Jan 16, 2021 11:50 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Memorizing relationship of Q and K
Replies: 9
Views: 71

Re: Memorizing relationship of Q and K

I like to think of it as mathematically. If you think about it, if Q is greater than K, then that means the numerator is larger than the numerator for K. As a result, Q has to generate more of the denominator in order to be equal to K. In other words, the chemical reaction needs to form more reactan...
by Vince Li 2A
Sat Jan 16, 2021 7:47 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Kw equation
Replies: 9
Views: 91

Re: Kw equation

Kw is the equilibrium constant for water, which is given to be 1x10^-14. I also just want to add that the reaction of autoprotolysis generates equal concentrations of H3O+ and OH-. Together, the two add to 14, which makes sense given the equilibrium constant for water. The main issue that comes with...
by Vince Li 2A
Sat Jan 16, 2021 7:38 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Non- water solvent
Replies: 7
Views: 53

Re: Non- water solvent

In general, you will assume that water is the universal solvent. If it is given in the problem that the states of the components are aqueous, then you know that the solvent is water. If a different solvent is used, I am sure that it will be given in the problem.
by Vince Li 2A
Sat Jan 16, 2021 7:35 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle with Temperature
Replies: 7
Views: 27

Re: Le Chatelier's Principle with Temperature

Think about it as if temperature is part of the reactants or products, depending on if the reaction is endothermic or exothermic. If the reaction is endothermic, then the temperature is in the reactants. If you add temperature (endothermic), then it will push the reaction forward, due to how you hav...
by Vince Li 2A
Thu Jan 07, 2021 7:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Constant Dependency
Replies: 2
Views: 26

Re: Equilibrium Constant Dependency

I mentioned this in another post, but I will say it again. We will get to this later in thermochemistry, but while a chemical reaction involves reactants and products, there is also the transfer of heat. Suppose a reaction was endothermic, and that you would add heat energy into the reactants to com...
by Vince Li 2A
Thu Jan 07, 2021 7:16 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Intermediate Values of K
Replies: 6
Views: 17

Re: Intermediate Values of K

I would assume that the intermediate values of K are what Dr. Lavelle would consider immeasurable, in that it is negligible to determine if the reactants or products are favored. You would have to perform a very in-depth analysis to see which side the reaction favors, but I feel like the same idea w...
by Vince Li 2A
Thu Jan 07, 2021 7:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Temperature and Kc
Replies: 4
Views: 27

Re: Temperature and Kc

This is beyond what we have learned at the moment, so I am using my high school chemistry concepts. In a reaction, there is the idea of the transfer of heat. A reaction could either be endothermic or exothermic, and temperature is another way of symbolizing heat. Let's say that you have a reaction t...
by Vince Li 2A
Thu Jan 07, 2021 7:06 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Positive and negative delta H
Replies: 5
Views: 28

Re: Positive and negative delta H

You have to remember to take the perspective of the reaction, which is the system. If the reaction is endothermic, you would gain energy, so a positive deltaH. If the reaction is exothermic, you would lose energy, so a negative deltaH. Kind of unrelated, but systems tend to prefer exothermic reactio...
by Vince Li 2A
Thu Jan 07, 2021 6:57 pm
Forum: Ideal Gases
Topic: Ideal Gas Law Question
Replies: 11
Views: 78

Re: Ideal Gas Law Question

Temperature is considered a constant, because we are assuming that the environment in which the reaction takes place is stable and unchanging, or else we wouldn't be able to solve for the others parts of the equation. The temperature will most likely be given in the problem.
by Vince Li 2A
Tue Dec 08, 2020 3:30 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Strong/Weak acids
Replies: 5
Views: 51

Re: Strong/Weak acids

What Savannah means AJ is that because as you go down a group, the electrons densities are farther away from the positive attraction from the nucleus. As a result, the "dilution" is due to the spread of the electrons around the atom. As a result, it is difficult for the atom to hold onto t...
by Vince Li 2A
Tue Dec 08, 2020 3:24 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Trichloroacetic acid example
Replies: 4
Views: 32

Re: Trichloroacetic acid example

pKa is the negative log of the Ka value, which is the dissociation constant for the reaction. The concentrations of the product are in the numerator which are multiplied together, and the concentrations of the reaction (most likely going to be just one value) is in the denominator. You can think of ...
by Vince Li 2A
Tue Dec 08, 2020 3:20 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: outline question on acid/base formula/structure
Replies: 4
Views: 48

Re: outline question on acid/base formula/structure

First, you should remember the strong acids and bases, and you should remember the exact definitions of an acid/base. There are 6 strong acids to remember, and 6 strong bases to remember. Knowing those, you should be able to determine other compounds that have a similar structure. For the definition...
by Vince Li 2A
Tue Dec 08, 2020 3:16 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: neutralization reactions
Replies: 5
Views: 60

Re: neutralization reactions

A neutralization reaction always includes an acid and a base reacting together to form a salt and water. It is important to note however that you can have ions in those acids and bases that then act as more acids and bases. For example, you can have an ion that reacts further to produce more H3O+ or...
by Vince Li 2A
Fri Dec 04, 2020 10:41 pm
Forum: Coordinate Covalent Bonds
Topic: Coordinate Covalent Bonds and Covalent Bonds
Replies: 7
Views: 95

Re: Coordinate Covalent Bonds and Covalent Bonds

Put simply, a coordinate covalent bond is when you have two atoms that are bonded covalently, however one atom donates an entire pair of electrons to make the bond. A regular covalent bond means that two atoms each share one electron to form a bond. The example provided in the lecture is an example ...
by Vince Li 2A
Sun Nov 29, 2020 10:02 pm
Forum: Hybridization
Topic: Hybridization
Replies: 3
Views: 20

Re: Hybridization

Hybridization accounts for the reason why you are able bond atoms to other atoms, due to the mixing of orbitals. Put in simple terms, provides an explanation as to why unpaired electrons in certain energy states are able to bond to other atoms. For example, it is why Carbon, which has only two lone ...
by Vince Li 2A
Sun Nov 29, 2020 9:54 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling #20
Replies: 6
Views: 78

Re: Sapling #20

I get where you’re coming from, it’s pretty complicated figuring out Lewis Structures, but I think it’s best if you take it one step at a time. 1. You should first count up the number of valence electrons you are dealing with. In this case it would be 32 electrons. 2. You know that pretty much no ma...
by Vince Li 2A
Sun Nov 29, 2020 9:43 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Nonpolar bonds
Replies: 7
Views: 52

Re: Nonpolar bonds

An example of a nonpolar bond would only be a diatomic molecule. I don’t think there would be any other non polar bond. I was confused about this too. It is also important to note that while the majority of bonds are polar, you can still have a non polar molecule. You just have to make sure that the...
by Vince Li 2A
Sun Nov 29, 2020 9:39 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond angles
Replies: 8
Views: 74

Re: Bond angles

Dr. Lavelle made sure to mention that we don’t need to know the exact bond angles. He just said to make sure that we know if the bond angles of one molecule are greater or less than another molecule. For example, knowing that the bond angle of a tetrahedral atomic shape is 109.5, if given a molecule...
by Vince Li 2A
Sun Nov 29, 2020 8:53 pm
Forum: Hybridization
Topic: hybridization, but very simple
Replies: 9
Views: 54

Re: hybridization, but very simple

Yup. One of the strategies I use to quickly determine the hybridization is by looking at how many bonding regions there are, and just go up by s, then p, then d. For example, for CH4, there are four bonding groups. As a result, it would be s and then p3. This adds to 4 bonding groups. It is importan...
by Vince Li 2A
Fri Nov 27, 2020 7:28 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Shape vs Polarity
Replies: 11
Views: 73

Re: Shape vs Polarity

Yes, I am pretty sure you are right. It does not really matter what the atoms are in terms of elements, the shapes will be the same. The only difference is as you mentioned, the polarities may differ. Let's say you had a Carbon atom that is bonded with a Cl, an H, an I, and an F. I don't know if it ...
by Vince Li 2A
Fri Nov 27, 2020 7:23 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: trigonal planar vs trigonal pyramidal
Replies: 9
Views: 64

Re: trigonal planar vs trigonal pyramidal

You can tell the difference between trigonal planar and trigonal pyramidal by looking at if there is a lone pair on the central atom that also has three other bonding regions with atoms. It can be tricky: they all have four electron density regions. As a result, you would say they are tetrahedral. H...
by Vince Li 2A
Tue Nov 24, 2020 11:58 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Negative Poles on Molecules
Replies: 2
Views: 13

Re: Negative Poles on Molecules

This is only one way and I am sure there are others, but typically the negative poles point towards atoms with the higher electronegativity. If you look at the example SO2 which has an electron density shape of trigonal planar, and angular in terms of molecular geometry, the dipole arrows would poin...
by Vince Li 2A
Tue Nov 24, 2020 11:52 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Sapling Question #1
Replies: 7
Views: 69

Re: Sapling Question #1

There's a difference between the electron density shape and the molecular geometry. The electron density shape in this case, you are right, is tetrahedral, due to how there are four densities of electrons: the lone pair on the S and the three locations of bonds. However, the electron density shape i...
by Vince Li 2A
Tue Nov 24, 2020 11:46 am
Forum: Determining Molecular Shape (VSEPR)
Topic: lone pair e-
Replies: 3
Views: 53

Re: lone pair e-

I get what the issue is. It's hard to really determine if a shape is polar and nonpolar just from looking at the lone pairs. In fact, I don't think there's any way to determine if the shape is polar or nonpolar just by looking at if the central atom has lone pairs. You have to identify the electron ...
by Vince Li 2A
Sat Nov 21, 2020 6:53 pm
Forum: Ionic & Covalent Bonds
Topic: How to determine which molecule is more ionic?
Replies: 11
Views: 124

Re: How to determine which molecule is more ionic?

Are you sure that NaCl is stronger than KCl? Just by looking at an electronegativity difference chart, I see that the difference for Na and Cl is 2.1 while the difference for K and Cl is 2.2 Perhaps the source in which you got the the information from is incorrect? I don't see how it would make sens...
by Vince Li 2A
Sat Nov 21, 2020 6:47 pm
Forum: Ionic & Covalent Bonds
Topic: Rules of ionization energy
Replies: 18
Views: 138

Re: Rules of ionization energy

The reason ionization energy increases from down to up and left to right on the periodic table is due to energy shells and shielding of electrons. To be more specific, as you go right across a period, the shell in itself is not increasing. So the electrons do not get farther away from the positively...
by Vince Li 2A
Sat Nov 21, 2020 6:41 pm
Forum: Ionic & Covalent Bonds
Topic: Molecule size and ionic character
Replies: 13
Views: 143

Re: Molecule size and ionic character

Interesting question, since I don't think Dr. Lavelle talked about this in his lecture. I don't know if this is right, but I assume that if you have more atoms in the molecule, it would affect the polarity of the molecule. If you have all of these atoms that have all of these interactions, surely th...
by Vince Li 2A
Sat Nov 21, 2020 6:32 pm
Forum: Ionic & Covalent Bonds
Topic: Polar Bonds
Replies: 19
Views: 140

Re: Polar Bonds

You would look at the dipoles of the molecules. Remember when Dr. Lavelle mentioned partial positive and partial negative charges. To determine if a molecule is polar, there are multiple strategies you can use. First, you could determine the Lewis dot structure. By looking at the dot structures, you...
by Vince Li 2A
Sat Nov 21, 2020 6:28 pm
Forum: Ionic & Covalent Bonds
Topic: Covalent Character
Replies: 33
Views: 240

Re: Covalent Character

Covalent character from ionic molecules is essentially which molecules express the most covalent character. Covalent character involves molecules that have a more larger electron density involving shared electrons. I saw that someone mentioned differences in electronegativity, which is true. The low...
by Vince Li 2A
Sat Nov 14, 2020 8:11 pm
Forum: Ionic & Covalent Bonds
Topic: Nomenclature
Replies: 6
Views: 28

Re: Nomenclature

I would agree, when I saw that question I was a little confused, because I didn't know what those molecules looked like. I think that Dr. Lavelle will not give us a question like that. He would give us the actual molecule, not the name for it, so I wouldn't worry about that.
by Vince Li 2A
Sat Nov 14, 2020 8:06 pm
Forum: Ionic & Covalent Bonds
Topic: London Dispersion Forces
Replies: 11
Views: 99

Re: London Dispersion Forces

This is what my high school teacher explained, and I use it to grasp the concept even further. It is not very scientific, but it helps me. Think of a nonpolar molecule. Obviously, there is no natural dipole (one side having slightly positive charge and another side having negative charge) in a nonpo...
by Vince Li 2A
Sat Nov 14, 2020 8:00 pm
Forum: Ionic & Covalent Bonds
Topic: Electronegativity
Replies: 18
Views: 112

Re: Electronegativity

I remember from in the lecture that Dr. Lavelle said that actually calculating the electronegativity is beyond the scope of this class. With regards to knowing electronegativities, the value will either be given to us in the question, or it will be in a sheet we can download. I am not sure which of ...
by Vince Li 2A
Sat Nov 14, 2020 7:57 pm
Forum: Ionic & Covalent Bonds
Topic: Sapling #13
Replies: 8
Views: 37

Re: Sapling #13

Yeah, it took me a while to figure this out, but here is what I learned: A hydrogen bond can bond with a highly electronegative atom at the lone pair location, and it can also bond to the slight positive hydrogen atoms. Based on looking at the molecule, you can see that there can be a hydrogen bond ...
by Vince Li 2A
Tue Nov 10, 2020 1:54 pm
Forum: Ionic & Covalent Bonds
Topic: "Favorable"
Replies: 4
Views: 36

Re: "Favorable"

Another way you can think of favorable is in terms of the state at which something most "wants to be in". There are many different ways of something being favorable. For example, take the halogens. They all "want" to complete their octet, in that all they need is to gain one more...
by Vince Li 2A
Thu Nov 05, 2020 10:04 pm
Forum: Dipole Moments
Topic: dipole dipole
Replies: 5
Views: 172

Re: dipole dipole

So the intermolecular forces are London Dispersions, Dipole-dipole, and Hydrogen Bonding. The intramolecular forces are ionic, metallic, and network solids. In terms of dipole-dipole and hydrogen bonding, a dipole-dipole bond is otherwise known as an attractive force between polar molecules, due to ...
by Vince Li 2A
Thu Nov 05, 2020 9:58 pm
Forum: Octet Exceptions
Topic: Expanded Octate
Replies: 4
Views: 37

Re: Expanded Octate

Hopefully one of the mods answers this, cause I am not too sure, but I think in one of the lectures, Dr. Lavelle said that everything past the 3p block and beyond can have an expanded octet, even including the elements way below. I maybe have heard incorrectly, but if I'm wrong let me know. Regardle...
by Vince Li 2A
Thu Nov 05, 2020 9:53 pm
Forum: Resonance Structures
Topic: Electron spin
Replies: 12
Views: 52

Re: Electron spin

There really isn't a way to determine if the electron is spinning +1/2 or -1/2. Pretty much the only practical reason why those two numbers exist is to communicate that the two electrons in the state are spinning in opposite directions, in that they are not parallel.
by Vince Li 2A
Thu Nov 05, 2020 8:33 pm
Forum: Resonance Structures
Topic: Delocalized e-
Replies: 5
Views: 52

Re: Delocalized e-

Delocalized electrons are electrons that are not associated iwth a single atom or covalent bond. In other words, that are electrons that are not localized to a specific area. As a result, delocalized electrons give the molecule additional stability, and it is delocalized electrons that are the reaso...
by Vince Li 2A
Thu Nov 05, 2020 8:30 pm
Forum: Ionic & Covalent Bonds
Topic: Bond Character
Replies: 6
Views: 39

Re: Bond Character

I remember how bond character is just another word for either ionic bond, covalent bond, or metallic bond. If you say that a molecule expresses ionic character, it is another word for just that molecule expresses ionic properties. The same goes for covalent character.
by Vince Li 2A
Fri Oct 30, 2020 10:55 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration
Replies: 5
Views: 34

Re: Electron Configuration

I do think that writing out the entire electron configuration can be very tiresome, so I think it depends on what the question asked, and the available answer choices. If it was a multiple choice, and you didn't see the noble gas configuration, then I guess you should write the full electron configu...
by Vince Li 2A
Fri Oct 30, 2020 10:51 pm
Forum: Quantum Numbers and The H-Atom
Topic: Spin state
Replies: 25
Views: 222

Re: Spin state

While Dr. Lavelle did show us an image of how two electrons were spinning in opposite directions, due to how one had an Ms = +1/2, and how another electron had an Ms = -1/2, I do remember how he told us that because we don't know exactly what the electrons look like, we only say that the electrons s...
by Vince Li 2A
Fri Oct 30, 2020 10:48 pm
Forum: Quantum Numbers and The H-Atom
Topic: Effective Nuclear Charge
Replies: 4
Views: 51

Re: Effective Nuclear Charge

Effective Nuclear Charge basically means the force the electron feels due to how the positively charged nucleus pulls the electrons towards it. However, because there are other electrons nearby, they essentially shield each other from the pull of the nucleus. I just searched this up, but the effecti...
by Vince Li 2A
Fri Oct 30, 2020 10:43 pm
Forum: Quantum Numbers and The H-Atom
Topic: Number of Electrons per Shell
Replies: 5
Views: 75

Re: Number of Electrons per Shell

Yes, Kyle is right. The s orbital carries at most 2 electrons, the p orbital carries at most 6 electrons, due to how there is the Px, Py, and Pz, three orientations for the energy level (two electrons per orientation you could say), and the d orbital carries 10 electrons, because there are 5 orienta...
by Vince Li 2A
Sun Oct 25, 2020 2:25 pm
Forum: DeBroglie Equation
Topic: Purpose of DeBroglie Equation
Replies: 11
Views: 128

Re: Purpose of DeBroglie Equation

The DeBroglie Equation is supposed to describe that objects with a very very small mass has a measurable wavelength. This can be figured out by just plugging in values. If you have a baseball that has a very large mass, if you plug a large value into the denominator, you will find that the wavelengt...
by Vince Li 2A
Sun Oct 25, 2020 12:37 pm
Forum: Quantum Numbers and The H-Atom
Topic: Energy Levels
Replies: 8
Views: 108

Re: Energy Levels

I feel like I have a general understanding of this. It is important to remember that everything is quantized. You either absorb the EXACT wavelength of light or you don't. There is no in between. As a result, if you absorb a frequency of light that is larger than what you want, supposing that the fr...
by Vince Li 2A
Sun Oct 25, 2020 12:34 pm
Forum: Quantum Numbers and The H-Atom
Topic: Magnetic Quantum Numbers
Replies: 6
Views: 37

Re: Magnetic Quantum Numbers

It makes sense, if you have an l=0, then you can only have one orientation because it is a sphere. If you have l = 1, you have three orientations, due to how there are 3 values that m sub l can be, such as the Px, Py, and Pz. The same goes with the d orbital, since there are 5 orientations it can be...
by Vince Li 2A
Sun Oct 25, 2020 12:28 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Angular Momentum Quantum number
Replies: 3
Views: 23

Re: Angular Momentum Quantum number

Yes, even if there was an l greater than 3, it would probably be out of our knowledge reach. Because we have only studied s, p, d, and f orbitals, we most likely would not go into when l is greater than 3.
by Vince Li 2A
Sun Oct 25, 2020 12:24 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: s and p Orbitals
Replies: 4
Views: 62

Re: s and p Orbitals

All of the orbital wave functions are organized in such a way that s orbitals are closer to the nucleus, p orbitals are farther from the s orbitals, d orbitals are farther away from the p orbitals. However, this distance gets smaller and smaller. In terms of energy, remember how we learned those equ...
by Vince Li 2A
Sun Oct 25, 2020 12:19 pm
Forum: *Shrodinger Equation
Topic: Last Equation on Equation Sheet
Replies: 5
Views: 39

Re: Last Equation on Equation Sheet

Yeah, if there are equations on the Equation Sheet that we haven't gone over, then I wouldn't worry about it. However, if he happens to include a question involving this equation, I am sure he will give us all of the numbers we need to solve the problem.
by Vince Li 2A
Thu Oct 15, 2020 11:43 pm
Forum: Properties of Electrons
Topic: Atomic Spectra and Energy levels
Replies: 4
Views: 75

Re: Atomic Spectra and Energy levels

Excited electrons move up and down energy levels when there is enough energy from an energy source to propel that electron to an "excited state". However, it is important to note that the energy source must be at a certain frequency to elevate that electron to the excited state. If the fre...
by Vince Li 2A
Thu Oct 15, 2020 11:24 pm
Forum: Trends in The Periodic Table
Topic: electronegative of the elements in the periodic table
Replies: 4
Views: 70

Re: electronegative of the elements in the periodic table

Yeah, I agree with Sophia. Basically, what the elements in the columns in the periodic table have in common are the valence electrons. Valence electrons are responsible for all of the chemical reactions that exist in the entire world FYI. If elements are in the same column, it means they have the sa...
by Vince Li 2A
Thu Oct 15, 2020 11:18 pm
Forum: Quantum Numbers and The H-Atom
Topic: atomic spectra
Replies: 7
Views: 72

Re: atomic spectra

Atomic spectra is basically the lines you get from electromagnetic radiation being emitted on an atom which display the relative wavelengths of the light as the atom's energy levels return to ground state. You see gaps in between the lines due to how everything is quantized, in other words not conti...
by Vince Li 2A
Thu Oct 15, 2020 11:08 pm
Forum: Photoelectric Effect
Topic: Frequency vs. Intensity
Replies: 16
Views: 133

Re: Frequency vs. Intensity

Light needs to be at a certain "frequency" in order to meet the threshold to eject electrons from the metal. If the light is not that frequency, then you can not eject electrons. However, suppose that the frequency meets the threshold energy, and electrons are ejected, then you can increas...
by Vince Li 2A
Thu Oct 15, 2020 11:03 pm
Forum: Properties of Electrons
Topic: Energy Gaps
Replies: 8
Views: 109

Re: Energy Gaps

It's basically electron shells. There really isn't any science to it. If there is, then it would be so in-depth that I definitely do not know. However, the electron shells basically means the distance away that the electrons are from the nucleus. As you go farther out from the nucleus, the energy le...
by Vince Li 2A
Tue Oct 13, 2020 1:45 pm
Forum: Properties of Electrons
Topic: Quanta vs Photons
Replies: 4
Views: 69

Re: Quanta vs Photons

I would have to agree with Grace, but I do think that the professor probably won't make us distinguish between the two. Those are very minute differences. In addition, I found a source that told me that you can use Quanta or Photons pretty interchangeably, so I would not sweat it too much. I do thin...
by Vince Li 2A
Fri Oct 09, 2020 9:16 pm
Forum: Properties of Light
Topic: Amplitude of Light Wave
Replies: 5
Views: 91

Re: Amplitude of Light Wave

Yes, the amplitude of the wave does indicate brightness/intensity. The frequency of the wave indicates color. In the context of the Photoelectric Effect, it is important for the frequency of the light to exceed a certain value for the metal having the light impinged on it in order to eject electrons...
by Vince Li 2A
Thu Oct 08, 2020 11:39 am
Forum: Limiting Reactant Calculations
Topic: Testing with a periodic table
Replies: 16
Views: 175

Re: Testing with a periodic table

I would assume so. I think that he may provide us with the equation sheet and constants in the problem as well, or there may be a hyperlink to a sheet full of constants. I don't know for sure though, I think he will clarify later on in the quarter.
by Vince Li 2A
Tue Oct 06, 2020 9:56 pm
Forum: Molarity, Solutions, Dilutions
Topic: Sapling homework number 10
Replies: 6
Views: 77

Re: Sapling homework number 10

Yeah, I pretty much assumed it as well. I did notice a little inconsistency when I did the problem. When I drew out the molecules and counted the number of Carbons on the reactant side and the product side, they didn't add up. I most likely did something wrong drawing the molecule, but it is possibl...
by Vince Li 2A
Tue Oct 06, 2020 9:39 am
Forum: Balancing Chemical Reactions
Topic: Combustion
Replies: 14
Views: 196

Re: Combustion

Yeah, I agree with nearly everything that has been mentioned. Combustion and burning always involves some type of hydrocarbon that is burned in O2 to always form CO2 and H20. In order to balance the chemical, you would have to look at the further information provided in the question. An example reac...

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