## Search found 103 matches

Fri Mar 12, 2021 1:33 pm
Forum: Method of Initial Rates (To Determine n and k)
Replies: 26
Views: 101

k is the reaction constant and tells us by how much that the rate is affected by the concentrations of the reactant beyond just looking that their orders (proportionality constant). The k value is lower at higher activation energies since the reactants tend to have less of an effect on the initial r...
Fri Mar 12, 2021 1:28 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: determining order [ENDORSED]
Replies: 7
Views: 87

### Re: determining order[ENDORSED]

It would be quite difficult to do that accurately since you don't know the magnitude of change that the concentrations of each reactant have on the initial rate law and it's only easy to tell whether or not the concentrations of the reactants have an effect on the initial rate law. Just divide the r...
Fri Mar 12, 2021 1:23 pm
Forum: General Rate Laws
Topic: Sapling Week 9/10 #2
Replies: 13
Views: 42

### Re: Sapling Week 9/10 #2

Since you are finding the rate law in terms of the concentration of B from the concentrations of A, you use the negative rate law of the concentration of a or -(-2 change in concentration of A/ change in time). Then you're good!
Fri Mar 12, 2021 1:20 pm
Forum: General Rate Laws
Topic: Sapling #5
Replies: 8
Views: 44

### Re: Sapling #5

I kinda use this general formula for these kinds of questions and its been quite helpful. (change in reactant)^n * (change in second reactant)^m...etc. = the change in the initial rate.
Fri Mar 12, 2021 1:17 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Gibbs Energy
Replies: 20
Views: 79

### Re: Gibbs Energy

So Gibbs free energy related to thermodynamics since it can tell us whether a reaction is spontaneous or nonspontaneous. If there is a negative Gibbs free energy there is some spontaneity to the reaction. We can also connect this to kinetics considering that if there is a spontaneous reaction that d...
Fri Mar 05, 2021 5:33 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Order of reaction
Replies: 16
Views: 111

### Re: Order of reaction

The order tells us the number of reactants participating in the reaction or that collide together simultaneously. Essentially, higher-order reactions are less likely to happen since they involve more reactants colliding together at precisely the same time (third order= three reactants colliding toge...
Fri Mar 05, 2021 5:29 pm
Forum: First Order Reactions
Topic: 1st Order Reactions
Replies: 25
Views: 122

### Re: 1st Order Reactions

So the straight line is essentially an exponential graph (differential rate law), but the natural log (integrated rate law) is taken of both sides to make it a clearly inversely proportional straight line that is easier to analyze.
Fri Mar 05, 2021 5:25 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Slowest step
Replies: 38
Views: 302

### Re: Slowest step

Think of it in terms of the example Lavelle gave to us about baking. The oven step is a known, set time at which we certainly know how long the baking will take place compared to the more variable steps of mixing the batter, etc. It tells us the minimum possible time the reaction will take place. It...
Fri Mar 05, 2021 5:18 pm
Forum: General Rate Laws
Topic: Integrated Rate Law
Replies: 7
Views: 28

### Re: Integrated Rate Law

So what it means by the product is in a different phase or is removed is that we only consider the forward reactions when analyzing the initial rates of reactions using the integration and rate laws. The rate law compares the concentration of reactant to the rate of the reaction and the integrated r...
Fri Mar 05, 2021 5:01 pm
Forum: General Rate Laws
Topic: k vs k'
Replies: 7
Views: 29

### Re: k vs k'

Yes. the k' represents the fact that we know the slope of the reactant and that the reactant is a first-order reaction since it fits a decreasingly proportional line. The k' can be used to find the true rate constant of the reaction which is k once the orders of the other reactants participating in ...
Fri Feb 26, 2021 5:18 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Electrochemical series
Replies: 3
Views: 31

### Re: Electrochemical series

An electrochemical series refers to the charts that we use to determine voltages of individual standard potentials between molecules. They are actually given a specific order based on their oxidating or reducing powers. The more negative the standard potential values, the better they act as a reduci...
Fri Feb 26, 2021 5:12 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Relationship between E naught and spontaneity
Replies: 8
Views: 55

### Re: Relationship between E naught and spontaneity

Yes, when the standard cell potential is more than zero, we expect the reactions to be favorable or spontaneous. Especially in all cases with galvanic cells which are always spontaneous. Also, we can say that if the standard potential is positive K>1 and the reactions favor products.
Fri Feb 26, 2021 5:09 pm
Forum: Balancing Redox Reactions
Topic: Oxidizing Vs Reducing agent
Replies: 22
Views: 76

### Re: Oxidizing Vs Reducing agent

I think of them as opposites of what they actually are if that makes sense. The reducing agent is what is being oxidized, and has a more negative individual standard potential and the oxidizing agent is the molecule that is being reduced (more positive individual standard potential).
Fri Feb 26, 2021 5:06 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Writing Cell Diagrams
Replies: 5
Views: 23

### Re: Writing Cell Diagrams

So for cell diagrams, the right side is always the cathode and the left side is always the anode. Specific molecules you put inside of the cell are only the ones being reduced (cathode) or oxidated (anode). You separate the reduced species from the oxidated using a salt bridge. Also, all solid elect...
Fri Feb 26, 2021 5:00 pm
Forum: Balancing Redox Reactions
Topic: Acidic vs. Basic
Replies: 20
Views: 74

### Re: Acidic vs. Basic

When you are balancing a redox reaction in a basic solution, you would do so as you would normally for an acidic solution (add H2O to balance oxygens and H+ to balance out any of the added hydrogens). However, there is the added step of adding OH- for every H+ you added (add this OH- on each side) a...
Fri Feb 19, 2021 4:43 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: delta U=nCvdeltaT
Replies: 4
Views: 44

### Re: delta U=nCvdeltaT

We use this equation because, at constant volume, the change in internal energy is equal to the q_v or the heat at a constant volume. Because q=c(delta T), we just use C_v,m as the heat capacity value.
Fri Feb 19, 2021 4:40 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta H and Delta S both positive
Replies: 31
Views: 118

### Re: Delta H and Delta S both positive

If both are positive, then the reaction is spontaneous only at high temperatures. This is because it's usually an endothermic reaction. The positive change in entropy value needs to be larger enough to make the change in free energy negative, which can be done by increasing the temperature.
Fri Feb 19, 2021 4:36 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Sapling (week 5 and 6) #2
Replies: 6
Views: 51

### Re: Sapling (week 5 and 6) #2

You probably found the number of joules produced in a second rather than an hour. Try cross multiplying or setting up a ratio essentially saying if in 1 second, (blank/answer in seconds from calc.)J produced, then in 3600 seconds (blank) J produced.
Fri Feb 19, 2021 4:32 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gas Constant R
Replies: 43
Views: 115

### Re: Gas Constant R

Yes, we usually use the gas constant so we can get our final value in moles. However, we use the 8.026 times 10^-2 value whenever we try to derive any values from the ideal gas equation since those values aren't in joules.
Fri Feb 19, 2021 4:27 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Is thermal mugs an example of an isolated system?
Replies: 38
Views: 157

### Re: Is thermal mugs an example of an isolated system?

Yes, they are considering that they don't exchange heat or energy with the surroundings (made to keep your beverage the same general temperature or do any work (change the mass of the substance in a container) since it has a lid.
Fri Feb 12, 2021 10:58 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy and volume in irreversible expansion
Replies: 2
Views: 24

### Re: Entropy and volume in irreversible expansion

So for irreversible reactions, they are usually free expansion problems. This way, the change in entropy of the system is the same as the change in entropy of the system of the reversible reaction and the change in the entropy of the surroundings is zero. Therefore the total change in entropy is equ...
Fri Feb 12, 2021 10:54 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Kelvin conversion
Replies: 40
Views: 125

### Re: Kelvin conversion

It says on the formula sheet that we use Celsius + 273.15, so that is usually what works for me.
Fri Feb 12, 2021 10:52 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneous as Written
Replies: 10
Views: 59

### Re: Spontaneous as Written

Yes, this could be due to two reasons, the change in entropy being positive (which makes sense since the more chaos or entropy you get, the more spontaneously it could have happened since that's how things naturally work) or due to the enthalpy change being more negative (so less order or enthalpy o...
Fri Feb 12, 2021 10:48 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Using Cp and Cv
Replies: 3
Views: 38

### Re: Using Cp and Cv

Yes, this is because they denote the heat capacities of the ideal gases at either constant pressure or volume. You only use heat capacity to calculate q for heat-related or temperature change problems (in this case change entropy due to temp. change).
Fri Feb 12, 2021 10:45 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Using 5/2 and 3/2
Replies: 6
Views: 50

### Re: Using 5/2 and 3/2

You are solving for two different values, the molar heat capacity at constant pressure and the molar heat capacity at a constant volume. The 5/2 and 3/2 correspond to different values. Note: these are only used for ideal gases.
Fri Feb 12, 2021 10:43 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: HW 4A.7
Replies: 4
Views: 12

### Re: HW 4A.7

Since you have to do two separate heat calculations for the copper kettle and then the water and add them together in part B. Just take the q value that you found for the water in part B and divide it by the value for total heat supplied in part a. That heat only corresponds to water itself.
Fri Feb 05, 2021 3:22 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: External Pressure
Replies: 32
Views: 105

### Re: External Pressure

I'm pretty sure the external pressure is what pushes the piston since when we have an open system, the pressure is constant pushing on the piston and the piston isn't moved unless it's through expansion or heat energy transfer.
Fri Feb 05, 2021 3:18 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: "Reversible" Reaction
Replies: 5
Views: 63

### Re: "Reversible" Reaction

I'm not too sure about this but I think it has to do with the idea that the external pressure can be adjusted to make changes in the system (it could expand or compress but doesn't have to stay that way since the pressure isn't constant).
Fri Feb 05, 2021 3:10 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Sapling Week 3 and 4 Question 14
Replies: 7
Views: 76

### Re: Sapling Week 3 and 4 Question 14

To find the moles of the ideal gas you have to use a different R-value since you are trying to end up with moles as your answer instead of J. Use 8.206*10^-2 L*atm/K*mol and rearrange to cancel out L, atm, and K.
Fri Feb 05, 2021 3:05 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Extensive vs intensive property for heat capacities
Replies: 7
Views: 37

### Re: Extensive vs intensive property for heat capacities

An extensive property is one that changes according to the amount of something you have and an intensive property is the exact opposite of that. An example is heat capacity. With a greater amount/ moles of a sample, the heat capacity or the amount of heat required to change the temperature of the sa...
Fri Feb 05, 2021 3:01 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Textbook Problem 4A.13
Replies: 3
Views: 33

### Re: Textbook Problem 4A.13

So for the second part, the formula to find the change in internal energy is the same as the formula for q since the internal energy is equal to q whenever the change in volume is constant. Since for the system: q= -(C_cal from calibration)(change in temp) q=-(0.487 kJ/deg. C)(3.57 deg C) q= change ...
Fri Jan 29, 2021 7:26 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: is HClO3 weak or strong? [ENDORSED]
Replies: 49
Views: 290

### Re: is HClO3 weak or strong?[ENDORSED]

It would be considered to generally be a strong acid considering that it has one less oxygen than a strong acid like perchlorate (HCLO4). The general rule of thumb is that whenever there is more oxygen, the acid is more strong considering its bonds become weaker and weaker to the point in which they...
Fri Jan 29, 2021 7:22 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cv and Cp
Replies: 16
Views: 101

### Re: Cv and Cp

It matters in questions involving calorimetry considering it tells you whether you can use the q value to find either the change in enthalpy (constant pressure) or the change in the internal temperature (constant volume/ bomb calorimeter). Sometimes you need to convert between the internal change in...
Fri Jan 29, 2021 7:14 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Sapling Q. #12 Heat Capacity Equation
Replies: 2
Views: 26

### Re: Sapling Q. #12 Heat Capacity Equation

For the first question, the per mole value for the heat of combustion is given so you would assume that the calculation is only for one mole of compound A and the heat capacity calculations. You are given the mass so find the heat or q using the number of moles and then convert the value to per gram...
Fri Jan 29, 2021 7:00 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Textbook problem 6.61
Replies: 7
Views: 33

### Re: Textbook problem 6.61

If you look at the state that the water is in, it is a liquid which means it doesn't impact the equilibrium constant in any way. This is because solids and liquids aren't reactive/ no smaller chemical reactions occur within them and they are usually present in excess.
Fri Jan 29, 2021 6:58 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Biological examples (ATP hydrolysis and osmotic pressure)
Replies: 5
Views: 72

### Re: Biological examples (ATP hydrolysis and osmotic pressure)

I would say that you would have to look this up since it was only briefly mentioned in the lecture. I know that ATP hydrolysis requires energy however since you need to break bonds to hydrolyze things which means a positive change in enthaply.
Fri Jan 29, 2021 6:49 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Significance of open, closed, isolated
Replies: 22
Views: 423

### Re: Significance of open, closed, isolated

Yes, it would be important to know which factors stay constant between a system and its surroundings. An open system is basically when both matter and energy and enter and exit the system (you can add moles of a substance or heat things up). A closed system is where the matter doesn't change but the...
Fri Jan 22, 2021 7:53 am
Forum: Phase Changes & Related Calculations
Topic: Phase Changes of Water Graph
Replies: 7
Views: 78

### Re: Phase Changes of Water Graph

The line just represents the heat's increase but not the direct or exact number. I would say the graph is just trying to represent a proportional relationship to the higher phase change and a higher temperature. The more heat or energy you have, the higher up the phase change (fusion to sublimation)...
Fri Jan 22, 2021 7:50 am
Forum: Phase Changes & Related Calculations
Topic: phase transition
Replies: 13
Views: 62

### Re: phase transition

The temperature is still constant since all of the heat goes into breaking the bonds of the material rather than physically heating up the material. That is why there is a constant line, which is basically the material transforming into another phase.
Fri Jan 22, 2021 7:48 am
Forum: Phase Changes & Related Calculations
Topic: Endothermic v. Exothermic
Replies: 107
Views: 393

### Re: Endothermic v. Exothermic

Yes, I would say so in my opinion but I don't know if there any exceptions out there. To be clear, sublimation, vaporization, and fusion all are endothermic to begin with and you have to add heat to the system for there to be a phase change from ice to steam, that is why they all have positive delta...
Fri Jan 22, 2021 7:41 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: What is Qp?
Replies: 5
Views: 59

### Re: What is Qp?

qp is basically representing the heat of the system so with a greater change in enthalpy or a positive change in enthalpy, the heat of the system increases, and it is an endothermic system. This is because the change in enthalpy usually refers to the system.
Fri Jan 22, 2021 7:37 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess Law
Replies: 10
Views: 201

### Re: Hess Law

For the Hess Law, we basically have to manipulate the equation so that it matches the specific final reaction we want. The real first step is to write the chemical formula for what the question wants and to balance it. Then, take the other formula given and create a formula in which the stoichiometr...
Fri Jan 15, 2021 5:21 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Gas
Replies: 16
Views: 120

### Re: Gas

Gases for the partial pressure use atm and bars interchangeably (since they are basically the same value/ a lot like Watts and Joules if that makes any sense). It's just that our books use bars rather than atm. more often.
Fri Jan 15, 2021 5:18 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: H2O as a Gas
Replies: 69
Views: 512

### Re: H2O as a Gas

Generally, you would include it if it was a gas and if it is NOT a solvent (meaning it is on both sides of the equation since (aq) means something + H2O).
Fri Jan 15, 2021 5:15 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: When x is negligible in Equilibrium constant
Replies: 34
Views: 196

### Re: When x is negligible in Equilibrium constant

According to the latest lecture, an easy way to determine this is if the K value is less than 10^-4 or if the x value is less than 5% of the initial value. I think just using the guideline of when K<10^-4 is better considering you won't have to find the x value from the approximation method first an...
Fri Jan 15, 2021 5:11 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Q and K on and reactant/product concentrations
Replies: 8
Views: 38

### Re: Q and K on and reactant/product concentrations

Actually, when Q<K it is always the case that the reaction is a forward reaction since more products are formed than reactants, so [P] is always greater than [R]. I don't get where you got the info that [R]> [P] when Q<K since [R] is decreasing. In the questions having to do with Le Chatelier's prin...
Fri Jan 15, 2021 5:04 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Using Kw
Replies: 5
Views: 31

### Re: Using Kw

We use Kw (1*10^-14) whenever we are dealing with the concentrations of hydronium and hydroxide ions, so basically when it comes to any reactions involving aqueous solutions. For instance, if we were asked for the hydronium concentration from the hydroxide concentration or if we were asked for their...
Fri Jan 08, 2021 9:10 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Part 3 Post Module Assessment #19
Replies: 4
Views: 32

### Re: Part 3 Post Module Assessment #19

Make sure that you divided the mole values of the products and reactants by the 3.00 liters of the vessel mentioned in the problem before you plug it into the icebox. This was a mistake I made the first time. Remember that the concentration is in moles per liter and not just moles. Hopefully, then y...
Fri Jan 08, 2021 9:06 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: K vs. Q in experiments
Replies: 2
Views: 55

### Re: K vs. Q in experiments

So to put it simply, K is when the reaction or system is at equilibrium and the concentrations of the reactants and products can be anything but they don't change further (for instance product concentrations can be greater than reactants or vice versa). What is important to note is that the concentr...
Fri Jan 08, 2021 9:00 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Water
Replies: 28
Views: 174

### Re: Water

Well, it depends on what state H2O (when it is in liquid form it cancels out) is in. However, I would like to add is that H2O can also be used as a solvent and is placed on both sides of the equation in liquid form so when you write the K constant the concentrations cancel out. When H2O is in gas fo...
Fri Jan 08, 2021 8:54 am
Forum: Ideal Gases
Topic: Chemical Equilibrium Part 1A Post-Module Assessment
Replies: 11
Views: 40

### Re: Chemical Equilibrium Part 1A Post-Module Assessment

The correct answer is that there is no reaction occurring (which is not true!). Whenever something is at equilibrium is means that there is no NET change of the concentrations of products and reactants but their values might slightly change due to small, almost unnoticeable perturbations. But, to be...
Fri Jan 08, 2021 8:51 am
Forum: Ideal Gases
Topic: Gas constant R
Replies: 26
Views: 163

### Re: Gas constant R

The constant of R is the ideal gas constant and you don't need to memorize anything regarding constants considering that they are all on the equations sheet. In terms of using the constant, the units tend to shift on whether you have the molar concentration (L*mol-1*K-1*atm)of something or you have ...
Mon Dec 07, 2020 8:16 am
Forum: Ionic & Covalent Bonds
Topic: Valence in d-block
Replies: 4
Views: 56

### Re: Valence in d-block

So when you are taking into account the d block, you would count its valence electrons just like you would do for the s and p block, just make sure that for the 4th period, you count the d-block as it overlaps with the s and p blocks at that rate. Now, the only thing you would do differently, in ter...
Mon Dec 07, 2020 8:09 am
Forum: Quantum Numbers and The H-Atom
Topic: n=6,l=5
Replies: 6
Views: 109

### Re: n=6,l=5

Theoretically, that would work considering that the l number is one less than the n number. l is always one less than the n number considering it is a subshell of it.
Mon Dec 07, 2020 8:07 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: d orbitals
Replies: 7
Views: 108

### Re: d orbitals

So basically, d orbitals are only present and empty in the elements from the 3rd period to beyond. This is especially useful to know for Lewis structures since that means the central atom can hold more than eight electrons forming something greater than an octet. The orbital itself has one node (whe...
Mon Dec 07, 2020 7:59 am
Forum: DeBroglie Equation
Replies: 21
Views: 176

Avogadro's number is approximated by 6.022*10^23 and it basically represents the number of atoms in a mole of any element which is different from the individual atomic mass. You can multiply the moles of something by Avogadro's number to get the atom amount of it. You can divide by Avogadro's number...
Mon Dec 07, 2020 7:55 am
Topic: What if I want to know more?
Replies: 2
Views: 69

### Re: What if I want to know more?

Black body radiation refers to the idea that if heated to various high temperatures, a black body (which cannot be seen) can emit different or multiple wavelengths of light. In this way, it connects more to the wave theory or wave property of electromagnetic radiation rather than the particle proper...
Mon Nov 30, 2020 8:32 am
Forum: Hybridization
Topic: Hybrid Orbitals
Replies: 7
Views: 76

### Re: Hybrid Orbitals

You can use hybrid orbitals to determine the amount of bonding that occurs between central atoms and some surrounding atoms. It's kind of a confirmation of the electron arrangement of the molecule and helps you see clearly if there are any pi or sigma bonds involved. You basically find the electron ...
Mon Nov 30, 2020 8:27 am
Forum: Hybridization
Topic: sp^3
Replies: 8
Views: 94

### Re: sp^3

It seems to be common considering that when you use the octet rule to complete a lewis structure, there are always four bonds between the central atom and the surrounding atom. In this way, if we consider the electron arrangement of the molecule in terms of the central atom, we will always get four ...
Mon Nov 30, 2020 8:23 am
Forum: Biological Examples
Topic: vitamin b-12
Replies: 3
Views: 141

### Re: vitamin b-12

Vitamin b-12 does contain the metal cobalt, which is what forms an octahedral complex with five ligands four nitrogens from an amine group, and one ligand from a CH2 group. It acts as a catalyst (as a result of the weak bonds between the carbon in the CH2 and the cobalt) and it helps to prevent illn...
Mon Nov 30, 2020 8:19 am
Forum: Biological Examples
Topic: Hemoglobin
Replies: 12
Views: 275

### Re: Hemoglobin

The biological importance is that it binds to an oxygen ligand, specifically through five bonding points (4 nitrogen atoms binding points that also connect to a central iron atom and one histidine binding site which also is through another nitrogen atom) in this way a red blood cell can deliver oxyg...
Mon Nov 30, 2020 8:11 am
Forum: Biological Examples
Topic: Cisplatin Bonding
Replies: 4
Views: 28

### Re: Cisplatin Bonding

There have to be two guanines in a row to allows for a stronger bond to form between the cisplatin's two Cl atoms rather than have one bond form between them. Guanines have a special structure that allows them to bond to the ligand in that way. This GGCC pattern tends to be a common one in all biolo...
Tue Nov 24, 2020 10:12 am
Forum: Determining Molecular Shape (VSEPR)
Topic: regions of electron density
Replies: 7
Views: 84

### Re: regions of electron density

I wouldn't overthink it too much but I would think that the areas of electron density are where there are clusters of electrons (especially lone pairs). Double and Triple bonds are just another cluster of electrons so they are only considered one region of electron density which is similar to any ot...
Tue Nov 24, 2020 10:04 am
Forum: Determining Molecular Shape (VSEPR)
Topic: lone pair e-
Replies: 3
Views: 56

### Re: lone pair e-

I don't think that lone pairs play a role in determining the polarity of a molecule directly. Like, having more lone pairs doesn't correlate to having more or less polarity. However, they DO influence the shape of the molecule and whether the dipole moments cancel out each other when there are polar...
Tue Nov 24, 2020 9:53 am
Forum: Hybridization
Topic: Lecture 23 question
Replies: 5
Views: 55

### Re: Lecture 23 question

The electrons that we count in Lewis structures directly translate into determining the shape of molecules and these electrons that we count are outer valence electrons. The 1s orbital isn't considered an outer shell and just forms the basis of how strong the ionization energy is compared to the siz...
Tue Nov 24, 2020 9:03 am
Forum: Sigma & Pi Bonds
Topic: Resonance and pi bonds
Replies: 3
Views: 61

### Re: Resonance and pi bonds

These are just my thoughts. Resonance structures, by definition, have a partial double bond character so all of the bond lengths are the same overall since they are a mixture or average of all the bond lengths of the lower energy Lewis structures. In this way, sigma and pi bonds wouldn't apply to th...
Tue Nov 24, 2020 8:50 am
Forum: Hybridization
Topic: 2F.1
Replies: 2
Views: 37

### Re: 2F.1

There isn't really the need to worry about the specifics but getting an understanding of the electron arrangement can aid in understanding the general orientation of the orbitals. The chart above is quite useful in this considering the orientation since the electron arrangements, or in order words, ...
Mon Nov 16, 2020 9:14 am
Forum: Coordinate Covalent Bonds
Topic: Lone Pairs and Lewis Bases
Replies: 4
Views: 65

### Re: Lone Pairs and Lewis Bases

In general, Lewis acids are electron-deficient and lone pairs on the central atom, especially excess ones if the central atom is a period 3 or greater element are a result of excess valence electrons so it's likely that the element is a base rather than an acid. Another kind of rule of thumb, Period...
Mon Nov 16, 2020 9:10 am
Forum: Dipole Moments
Topic: Strength of intermolecular forces
Replies: 3
Views: 51

### Re: Strength of intermolecular forces

Distance plays a huge role in determining the strength of dipole-dipole interactions since this increases the bond length between them making the interactions weaker (the measure of the interactions is divided by the distance cubed). If the dipole was interacting with an ion, however, there is a gre...
Mon Nov 16, 2020 9:01 am
Forum: Formal Charge and Oxidation Numbers
Topic: Sapling Cl Oxidation Number
Replies: 2
Views: 25

### Re: Sapling Cl Oxidation Number

The oxidation number for the Chlorine is actually 7 considering that the sum of the oxidation numbers of each element adds up to the charge and oxygen has an oxidation number of -2. We have four oxygen as well so 4(-2)= 8 + _=-1. There has to be an oxidation number of 7 to make the charge -1. Since ...
Mon Nov 16, 2020 8:54 am
Forum: Bond Lengths & Energies
Topic: Bond Length
Replies: 5
Views: 46

### Re: Bond Length

I've noticed that for bond length reference points it tends to vary based on the example you are looking at in terms of homework questions. There will usually be a table given to you of the experimental bond lengths compared to the actual bond lengths of the Lewis structure you are looking at. In th...
Mon Nov 16, 2020 8:48 am
Forum: Electronegativity
Topic: Homework Problem 3F.19
Replies: 4
Views: 31

### Re: Homework Problem 3F.19

a.) Xenon is larger than Argon in terms of the atomic radius so it's bound to have more LDF forces since a bigger electron cloud is easy to be distorted b.) There is more of a rod-like structure for diethyl along with its hydrogen bonds so it has more extensive LDF forces as well. C.) Again, the rod...
Mon Nov 09, 2020 8:27 am
Forum: Octet Exceptions
Topic: expanded octet in d orbital
Replies: 4
Views: 31

### Re: expanded octet in d orbital

So elements with an expanded orbital, meaning that they could potentially hold more electrons in a Lewis structure, has to do with the fact that the d-orbital allows for extra space of up to 10 valence electrons. Looking at the periodic table, we see that elements that are before Period 3 tend to ha...
Mon Nov 09, 2020 8:21 am
Forum: Formal Charge and Oxidation Numbers
Topic: Calculating Formal Charge
Replies: 9
Views: 107

### Re: Calculating Formal Charge

Adding up the formal charges of the atoms of a molecule should give you the overall oxidation number if that's what you mean, but NOT the net formal charge. You will need to calculate the individual formal charges of each atom in order to understand if they have the correct configuration of electron...
Mon Nov 09, 2020 8:13 am
Forum: Ionic & Covalent Bonds
Topic: Electron Affinity
Replies: 8
Views: 83

### Re: Electron Affinity

Electron affinity is the measure of how much an element wants an electron. Elements that are the closest to becoming a noble gas have a high electron affinity since they want to complete their octet more than any of the other elements before it. It can be calculated by finding the difference between...
Mon Nov 09, 2020 8:07 am
Forum: Ionic & Covalent Bonds
Topic: Size of Bonds
Replies: 28
Views: 128

### Re: Size of Bonds

Double bonds are shorter considering that they are stronger bonds since the distance between the nuclei of two atoms is smaller. Single bonds are weaker than double bonds, considering the distance between their nuclei is larger. It takes more energy to break apart double bonds compared to single bon...
Mon Nov 09, 2020 8:04 am
Forum: Ionic & Covalent Bonds
Topic: Difference Between Ionic & Covalent Bonds
Replies: 11
Views: 73

### Re: Difference Between Ionic & Covalent Bonds

Ionic bonds are usually between elements that differ greatly in electronegativity or very opposite sides of the periodic table. Professor Lavelle told us that we would get a table with the electronegativity values so this could be helpful in determining something is an ionic bond. When it comes to L...
Mon Nov 02, 2020 7:59 am
Forum: Lewis Structures
Topic: Brackets for Anions
Replies: 6
Views: 115

### Re: Brackets for Anions

The brackets are used for other species, basically any ions like cations AND anions. This is the same in covalent and ionic bonding. If you end up starting off with two ions and covalently bond them, you will have brackets around the final Lewis structure since they maintain their charge. If you tra...
Mon Nov 02, 2020 7:54 am
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge
Replies: 11
Views: 398

### Re: Formal Charge

The charge would just be the result that you get directly from your equation, which is -1 in this case. Just because it's an electron doesn't make a difference since the equation only applies to electrons and with that reasoning and the equation, there is no way we will ALWAYS get a negative number.
Mon Nov 02, 2020 7:48 am
Forum: Electronegativity
Topic: Periodic Table Trend
Replies: 37
Views: 441

### Re: Periodic Table Trend

So the trend for ionization energy basically corresponds to the atomic radius of the element. The bigger the atomic radius, the lower the ionization energy. The atomic radii decrease along a period and increase down a group. SO we can say the ionization energy increases down a period and decreases d...
Mon Nov 02, 2020 7:39 am
Forum: Resonance Structures
Topic: Delocalization
Replies: 6
Views: 298

### Re: Delocalization

So, delocalization usually occurs with elements that have covalent bonds that can contribute to resonance. Certain lewis structures of the same compound or molecule are lower energy than others and we ideally want the lowest energy combination, which is explored with the concept of formal charge but...
Mon Nov 02, 2020 7:34 am
Forum: Ionic & Covalent Bonds
Topic: Differences in structures between ionic and covalent bonds
Replies: 7
Views: 77

### Re: Differences in structures between ionic and covalent bonds

The bonds are drawn the same way in terms of Lewis structures as the electron pairs are represented as dots. However, when you are drawing ionic bonds, the are no shared electrons represented but electrons are transferred from one "to be" cation to an anion that gains electrons. Both bonds...
Mon Oct 26, 2020 9:32 am
Forum: Empirical & Molecular Formulas
Topic: Dealing with Diatomic Elements
Replies: 11
Views: 144

### Re: Dealing with Diatomic Elements

For this question think about it in the context of the problem and that helped me a lot because I was struggling with the same thing. When you find the moles of each element you need to convert them in terms of one mole for the sake of the empirical formula you will write but the nitrogen produced f...
Mon Oct 26, 2020 9:20 am
Forum: Limiting Reactant Calculations
Topic: Excess reactant affecting limiting reactant
Replies: 7
Views: 130

### Re: Excess reactant affecting limiting reactant

Yes. It can be assumed that the oxygen is in excess means that the other reactant is what is limiting since all of it is being used up in the reaction rather than the reactant oxygen being not totally used up. For some of the questions we did, they just give you the weight of a single reactant, that...
Mon Oct 26, 2020 9:06 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Clarification on the "uncertainty" part of this equation
Replies: 7
Views: 137

### Re: Clarification on the "uncertainty" part of this equation

The uncertainty part comes from the fact the we don't know the change in velocity of the electron from area to another, because we know the time takes to travel from one distance to another but NOT the distance itself (velocity= distance/time). This is due to the fact that an electron is so small in...
Mon Oct 26, 2020 8:58 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 2 orbitals occupied
Replies: 1
Views: 22

### Re: 2 orbitals occupied

I may not answer your question fully but this is what I am getting. You are on the right track in your thinking. These "orbitals" that you calculated from n=2 are correct. However, they refer to separate subshells which have their own number of orbitals of which the electrons (two per orbi...
Mon Oct 26, 2020 8:47 am
Forum: Quantum Numbers and The H-Atom
Topic: Spin Magnetic Quantum Number
Replies: 6
Views: 58

### Re: Spin Magnetic Quantum Number

For the spin magnetic quantum number, the +1/2 indicates up and the -1/2 indicates down. We were never taught how to actually calculate the spin, but there is some conceptual knowledge about how it was discovered in the first place which could guide your understanding. The Stern and Gerlach experime...
Mon Oct 26, 2020 8:40 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Electrostatic Potential Energy
Replies: 1
Views: 18

### Re: Electrostatic Potential Energy

Electrostatic potential energy can just be thought as the amount of energy a particle retains relative to the outside forces it is facing. It is influenced by mainly two things: repulsion forces and attraction forces of the nucleus referred to as nuclear charge. Repulsion forces are between two elec...
Mon Oct 26, 2020 8:23 am
Forum: DeBroglie Equation
Topic: Circular Standing Waves around Atoms
Replies: 2
Views: 49

### Re: Circular Standing Waves around Atoms

Circular standing waves are just a model of how electrons can change their energy states in a oscillating fashion. Stable circular standing waves implies that the electron has enough energy, possibly from a photon, to make an energy change (delta E) that is equivalent to the energy change between n=...
Mon Oct 19, 2020 8:24 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Orbitals
Replies: 4
Views: 177

### Re: Orbitals

Finding the number of orbitals doesn't have a short cut to my knowledge, but it's not super hard to do. Know that l=0 is an s orbital, l=1 is a p, l=2 is a d orbital, and l=3 is an f-orbital. so, spdf. Btw, we get the l from the n or the shell number and l always is less than n. So for n=2 , for ins...
Mon Oct 19, 2020 8:10 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configurations that dont follow the pattern
Replies: 3
Views: 27

### Re: Electron Configurations that dont follow the pattern

So the elements that don't follow up the "building up principle" rules are: Mo, Cu, Cr, Ag, and Au. This is due to the fact that an electron from one of the orbitals moves to the other orbital to pair with its unpaired electron. If you were to do the electron configuration for Cu for insta...
Mon Oct 19, 2020 8:01 am
Forum: Photoelectric Effect
Topic: Atomic Specta Post-Module Assessment
Replies: 3
Views: 50

### Re: Atomic Specta Post-Module Assessment

You wouldn't need to use Avogadro's number, in this case, considering "Sodium atom" just refers to the electron being removed from something and not the number of atoms. Also, we use Avogadro's number to find the number of moles through division and the number of atoms through multiplicati...
Mon Oct 19, 2020 7:50 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Shape of Orbitals?
Replies: 6
Views: 181

### Re: Shape of Orbitals?

I'm pretty sure the whole orbital shape stuff is just to help with the conceptual understanding of the topic, you just have to understand the number of electrons in each orbital, the subshells, the principal quantum numbers, and electron spin. The shape of the orbital itself will not be asked about ...
Mon Oct 19, 2020 7:39 am
Forum: Einstein Equation
Topic: Sapling #5
Replies: 7
Views: 106

### Re: Sampling #5

At first glance, this is what I would do. I would use the wavelength in m (convert cm to using 10^-2) and then plug in just Planck's constant, the constant speed of light, and the wavelength given into the E=hC/wavelength equation. Once I get the number of Joules (E) of energy the photon can potenti...
Tue Oct 13, 2020 8:31 am
Forum: Empirical & Molecular Formulas
Topic: Empirical and Molecular Formulas
Replies: 9
Views: 154

### Re: Empirical and Molecular Formulas

I don't think the website meant the exact "same thing". You're right, the empirical formula is the relative number (ratio) of atoms per element and the molecular formula is the exact number of the atoms in the context of the actual balanced equation or experiment in a lab. However, they ar...
Tue Oct 13, 2020 8:22 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Textbook Problem E.15 [ENDORSED]
Replies: 3
Views: 121

### Re: Textbook Problem E.15[ENDORSED]

To put it simply, this problem is asking you to basically find a type of metal, add sulfur to that metal, and then find the molar mass of that metal and the sulfur. 1.) subtract the molar masses of hydrogen and oxygen from the total molar mass given. 2.) find an element on the periodic table that ha...
Tue Oct 13, 2020 8:15 am
Forum: SI Units, Unit Conversions
Replies: 12
Views: 135

Avogadro's number represents the number of atoms/formula units/molecules in a mole. So it can be denoted as 6.002 * 10^23 atoms/mole. You can use Avogadro's number to find the number of atoms of something in a mole form, essentially converting moles to atoms. Note: every element has the same number ...
Tue Oct 13, 2020 8:10 am
Forum: Photoelectric Effect
Topic: Photoelectric Effect original purpose
Replies: 6
Views: 35

### Re: Photoelectric Effect original purpose

The main question that fueled the set up of the "photoelectric experiment" was to answer the questions how "how different were the work functions or as they called it "threshold potentials" between the different elements?". To answer these questions, metal plates were t...
Tue Oct 13, 2020 7:55 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: How to know whether answer is in mols or atoms
Replies: 5
Views: 120

### Re: How to know whether answer is in mols or atoms

Firstly, the "amount" always refers to the moles of something, so you know your answer will not have to be multiplied by Avogadro's number to cancel out the moles for atoms/molecules/formula units which are the same things by the way. The amount never refers to atoms so multiplying moles t...
Mon Oct 05, 2020 5:49 pm
Forum: Balancing Chemical Reactions
Topic: Reaction Terminology "In excess"
Replies: 11
Views: 135

### Re: Reaction Terminology "In excess"

If it states "in excess" it refers to the fact that one of the reactants is not the limiting reactant so in excess DOES refer to the reactant. I notice it's common to have a problem analyzing the limiting reactants or anything related to the reactants with combustion reactions.