Search found 101 matches

by Vicki Liu 2L
Mon Mar 09, 2020 11:36 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Adding a Catalyst
Replies: 6
Views: 123

Re: Adding a Catalyst

It is true that adding a catalyst speeds up a reaction, but it does not change the equilibrium concentrations because K remains a constant (unless temperature changes). Kinetics focuses only on the rate at which equilibrium is reached; the equilibrium condition itself is left unchanged.
by Vicki Liu 2L
Mon Mar 09, 2020 11:18 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: reaction rate vs average reaction rate
Replies: 5
Views: 69

Re: reaction rate vs average reaction rate

Mathematically, there is a difference in which initial rate and average rate are solved/represented: Average rate = change in [A] / change in time (for two distant points) Initial rate = d[A]/dt (where d represents a very small deviation) Note that initial rate is the one you would use the rate law ...
by Vicki Liu 2L
Mon Mar 09, 2020 11:12 am
Forum: First Order Reactions
Topic: Deriving First Order Half Life Equation
Replies: 3
Views: 28

Re: Deriving First Order Half Life Equation

This traces back to the definition of half-life, which is the time at which the concentration is half its initial. In other words [A] is 0.5 times its initial, [A]0. As for the t(1/2), this is just a way to denote the half-life.
by Vicki Liu 2L
Mon Mar 09, 2020 11:07 am
Forum: *Free Energy of Activation vs Activation Energy
Topic: Explanation of Pseudo Equilibrium Constant
Replies: 1
Views: 46

Re: Explanation of Pseudo Equilibrium Constant

The pseudo equilibrium constant allows you to keep track of a stage of the reaction, focusing on an intermediate rather than the final product. For example, given the equilibrium reaction A + B <--> AB <--> C, the pseudo equilibrium constant would be the ratio of [AB]/[A][B].
by Vicki Liu 2L
Mon Mar 09, 2020 11:02 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Reactant order
Replies: 4
Views: 54

Re: Reactant order

Once you use other experiments to figure out the order with respect to B and C, you can plug an actual value into the exponents for their concentrations instead of needing to cancel them out. By doing this, the order with respect to A would be the only variable that needs solving still. Hope this he...
by Vicki Liu 2L
Mon Mar 02, 2020 11:22 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Different types of galvanic cells
Replies: 2
Views: 36

Re: Different types of galvanic cells

To add onto what was said above, electrolytic cells take electrical energy and convert it to chemical energy to drive reactions.
by Vicki Liu 2L
Mon Mar 02, 2020 11:21 am
Forum: Balancing Redox Reactions
Topic: Anode and Xathod
Replies: 9
Views: 63

Re: Anode and Xathod

Another difference to note is that usually the anode will decrease in solid mass while the cathode will increase in solid mass. This is because at the anode, solid metal atoms are oxidized into their aqueous ion form. At the cathode, ions are reduced into their solid metal form. Thus, you would obse...
by Vicki Liu 2L
Mon Mar 02, 2020 11:16 am
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: Metal in a Solution
Replies: 3
Views: 73

Re: Metal in a Solution

There is a set of solubility rules that allows you to predict whether metal compounds will dissociate. For instance, compounds containing group 1 ions are always soluble. A more comprehensive list can be found online. Hope this helps!
by Vicki Liu 2L
Mon Mar 02, 2020 11:13 am
Forum: Balancing Redox Reactions
Topic: Oxidation/Reduction
Replies: 17
Views: 219

Re: Oxidation/Reduction

Generally, you consider just the atom in terms of finding the change in oxidation number. However, when writing the actual half-reaction, you use the whole molecule because it cannot be separated (unless it's a soluble ionic compound).
by Vicki Liu 2L
Mon Mar 02, 2020 11:11 am
Forum: Method of Initial Rates (To Determine n and k)
Topic: Order
Replies: 5
Views: 62

Re: Order

Reaction order is essentially the power to which a reactant concentration is raised in order to give an accurate relationship between it and the rate of the overall reaction.
by Vicki Liu 2L
Mon Feb 24, 2020 11:55 am
Forum: Balancing Redox Reactions
Topic: Oxidizing/Reducing Agent
Replies: 8
Views: 77

Re: Oxidizing/Reducing Agent

Another way to think about it that may make sense is that the oxidizing agent is what causes something to be oxidized. To do this, it would have to gain the electron and thus is reduced. On the other hand, the reducing agent is what causes something to be reduced and therefore, has to give up an ele...
by Vicki Liu 2L
Mon Feb 24, 2020 11:53 am
Forum: Balancing Redox Reactions
Topic: 6K.3 part d
Replies: 3
Views: 46

Re: 6K.3 part d

I also had trouble with this problem, so I checked the solution manual and it seems the product should be Cl- instead of Cl2. Hope this helps!
by Vicki Liu 2L
Mon Feb 24, 2020 11:49 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt bridge
Replies: 6
Views: 76

Re: Salt bridge

To add on, without the salt bridge, the reaction would quickly reach equilibrium and come to a halt. In this sense, the salt bridge allows the flow of ions to maintain the charges needed for electron transfer to continue.
by Vicki Liu 2L
Mon Feb 24, 2020 11:43 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: What does the nitrate do in a concentration cell?
Replies: 6
Views: 99

Re: What does the nitrate do in a concentration cell?

I believe nitrate is a spectator ion in this case. In other words, AgNO3 was dissolved to achieve Ag+ ions in solution but the NO3- is not involved in the actual reaction.
by Vicki Liu 2L
Mon Feb 24, 2020 11:39 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Usage for Nernst equation
Replies: 7
Views: 167

Re: Usage for Nernst equation

The Nernst equation is used to determine the nonstandard cell potential. Given the standard cell potential, you can use the equation to determine how cell potential changes in relation to temperature and concentrations of the species.
by Vicki Liu 2L
Tue Feb 18, 2020 3:32 pm
Forum: Balancing Redox Reactions
Topic: Half Reactions
Replies: 7
Views: 54

Re: Half Reactions

Splitting redox reactions into half reactions makes it easier to study what is going on. In the overall reaction, electrons are not included but when you separate it into half reactions, you can see more clearly which reactant donates and which loses electrons. I don't think we would be given redox ...
by Vicki Liu 2L
Tue Feb 18, 2020 3:30 pm
Forum: Balancing Redox Reactions
Topic: Oxidation Numbers
Replies: 2
Views: 26

Re: Oxidation Numbers

There are some general rules you follow which allow you to determine most oxidation numbers. Here's a chart that summarizes this information. Hope it helps!
by Vicki Liu 2L
Tue Feb 18, 2020 3:27 pm
Forum: Balancing Redox Reactions
Topic: Reducing/Oxidizing Agent
Replies: 4
Views: 32

Re: Reducing/Oxidizing Agent

Reducing agent is what does the reducing. In other words, it's what causes something to gain an electron. It does so by losing an electron itself.
Along the same lines, the oxidizing agent causes something to lose an electron, thus gaining one itself.
by Vicki Liu 2L
Tue Feb 18, 2020 3:25 pm
Forum: Van't Hoff Equation
Topic: Units of Partial Pressure in 5G-13, 5G-15
Replies: 3
Views: 36

Re: Units of Partial Pressure in 5G-13, 5G-15

Actually, I think 1 bar is approximately equal to 1 atm, so it should give you the same answer. Online it says 1 bar = 0.986923 atm.
by Vicki Liu 2L
Tue Feb 18, 2020 3:23 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: delta vs. delta naught
Replies: 3
Views: 53

Re: delta vs. delta naught

The naught simply indicates that the values of G, H, and S are measured at STP conditions (1 atm and 273 K).
by Vicki Liu 2L
Mon Feb 10, 2020 11:42 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: How do you change the internal energy of an ideal gas?
Replies: 3
Views: 39

Re: How do you change the internal energy of an ideal gas?

I believe one way to change the internal energy of an ideal gas is by manipulating the temperature, as this changes the enthalpy of the system.
by Vicki Liu 2L
Mon Feb 10, 2020 11:38 am
Forum: Phase Changes & Related Calculations
Topic: Reversible or Irreversible
Replies: 5
Views: 51

Re: Reversible or Irreversible

I believe you would be able to deduce whether the question refers to a reversible or irreversible expansion based on the information given. For instance, if external pressure is constant, it would be irreversible.
by Vicki Liu 2L
Mon Feb 10, 2020 11:26 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Exothermic reactions
Replies: 5
Views: 39

Re: Exothermic reactions

Conceptually, it makes sense for exothermic reactions to be spontaneous as the release of energy makes the system more stable. Endothermic reactions on the other hand require an input of energy and thus, are not naturally occurring.
by Vicki Liu 2L
Mon Feb 10, 2020 11:25 am
Forum: Phase Changes & Related Calculations
Topic: Reversible and Irreversible
Replies: 3
Views: 39

Re: Reversible and Irreversible

Reversible expansions occur very slowly over an infinite amount of time so that equilibrium is not disturbed. Irreversible expansions occur rapidly and disturb equilibrium. Because of this, reversible expansions require much more work.
by Vicki Liu 2L
Mon Feb 10, 2020 11:18 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Spontaneity and Entropy
Replies: 3
Views: 40

Re: Spontaneity and Entropy

This question can also be considered more conceptually using the second law of thermodynamics. Since the entropy of the universe is always increasing, you can think of processes that increase entropy as naturally occurring, or spontaneous. However, whether or not delta G is actually negative depends...
by Vicki Liu 2L
Tue Feb 04, 2020 4:05 pm
Forum: Calculating Work of Expansion
Topic: second equation
Replies: 8
Views: 52

Re: second equation

I believe the integral was just involved in the process of deriving the equation.
by Vicki Liu 2L
Tue Feb 04, 2020 4:03 pm
Forum: Calculating Work of Expansion
Topic: Knowing which equation to use
Replies: 3
Views: 38

Re: Knowing which equation to use

It makes sense that S and H increase together because at higher temperatures, molecules move more quickly and thus have more disorder. This makes sense as gases have both high temperature and entropy values.
by Vicki Liu 2L
Tue Feb 04, 2020 3:51 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: heat given off by rxn = - heat absorbed by solution
Replies: 6
Views: 74

Re: heat given off by rxn = - heat absorbed by solution

I believe it is not important which side the negative sign is on, as long as you know the heat given off and absorbed are equal in magnitude but opposite signs.
by Vicki Liu 2L
Tue Feb 04, 2020 3:46 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: overall definitions
Replies: 4
Views: 46

Re: overall definitions

Adding on, Cp refers to molar heat capacity at constant pressure and Cv refers to molar heat capacity at constant volume. Both are for gases.
by Vicki Liu 2L
Tue Feb 04, 2020 3:18 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: molar entropy
Replies: 2
Views: 42

Re: molar entropy

First, you would compare the phases the substances are in at that temperature. Remember that gases have the highest entropy, followed by liquids, then solids. Next, if they are in the same phase, larger and complex molecules have higher entropy than smaller and simpler molecules.
by Vicki Liu 2L
Tue Jan 28, 2020 2:52 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Neutralization Reactions
Replies: 2
Views: 26

Re: Neutralization Reactions

I think using the specific heat capacity of water is valid for neutralization reactions is valid because you essentially assume that a solution of strong acid and strong base mixes to become neutral water. I'm not sure if it would work for weak acids and weak bases as well.
by Vicki Liu 2L
Tue Jan 28, 2020 2:48 pm
Forum: Phase Changes & Related Calculations
Topic: 4A.9
Replies: 4
Views: 29

Re: 4A.9

I first set up the equation -q(copper) = +q(water) since the amount of energy released by copper is absorbed by water. Then, you just plug in the respective values for mass and specific heat capacity on both sides of the equation. For temperature change, it's important to note that the final tempera...
by Vicki Liu 2L
Tue Jan 28, 2020 2:41 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Adding Enthalpies
Replies: 5
Views: 35

Re: Adding Enthalpies

It's important to point out that the reason why adding enthalpies is valid is because enthalpy is a state function, meaning it doesn't depend on the pathway.
by Vicki Liu 2L
Tue Jan 28, 2020 2:39 pm
Forum: Phase Changes & Related Calculations
Topic: Change in Temperature
Replies: 10
Views: 51

Re: Change in Temperature

To figure out the reasoning behind the change in equilibrium constant, figure out if heat is a product (exothermic reaction) or a reactant (endothermic reaction). When heat is added, the reaction will shift towards the opposite side. Then, based on whether the reactant or product side is favored, yo...
by Vicki Liu 2L
Tue Jan 28, 2020 2:36 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Best Method of the 3 Given?
Replies: 7
Views: 55

Re: Best Method of the 3 Given?

I don't think there necessarily is a "best" method because it depends on what information you are given for each problem. In class, Method 2 (bond enthalpies) was described as the least accurate, so avoid it when you can. But as long as you know which method to use to apply what's given, y...
by Vicki Liu 2L
Tue Jan 21, 2020 3:30 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Acids and Bases
Replies: 7
Views: 59

Re: Acids and Bases

I think one clue is a molecule’s charge. Acids are proton donors so they tend to be positive. Bases are proton acceptors so they tend to be negative.
by Vicki Liu 2L
Tue Jan 21, 2020 3:16 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Checking the approximation of "x"
Replies: 4
Views: 29

Re: Checking the approximation of "x"

It is impacted by stoichiometric coefficients. The approximation is valid if the percent dissociation is less than 5%. Thus you would have to compare the equilibrium concentration of product to the initial concentration of reactant. When calculating the equilibrium concentration of product, you woul...
by Vicki Liu 2L
Tue Jan 21, 2020 3:11 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: H2O in K Expressions
Replies: 6
Views: 44

Re: H2O in K Expressions

H2O as a gas should be included because changes to its partial pressure are notable. As a liquid, however, H2O is present in excess and there is essentially no change in its concentration before and after reaching equilibrium.
by Vicki Liu 2L
Tue Jan 21, 2020 3:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Approximation
Replies: 6
Views: 40

Re: Approximation

The logic behind this is that if K is sufficiently small, then very little of the species dissociates. Thus, the concentration is essentially unchanged.
by Vicki Liu 2L
Tue Jan 21, 2020 3:05 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5G.9
Replies: 1
Views: 15

Re: 5G.9

K is the same regardless of the concentration because the ratio of products to reactants at equilibrium stays constant. So when concentrations change, the reaction will shift to achieve that ratio. K only changes when the temperature of the system changes.
by Vicki Liu 2L
Tue Jan 14, 2020 2:38 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Autoprolysis
Replies: 9
Views: 125

Re: Autoprolysis

Wendy Perez 1E wrote:Adding to this conversation, what does amphiprotic mean again?


Amphiprotic means that a species can accept or donate a proton / H+.
by Vicki Liu 2L
Tue Jan 14, 2020 2:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homework 5g.1 B
Replies: 2
Views: 29

Re: Homework 5g.1 B

Increasing the concentration of the products affects the equilibrium reaction in that it causes the reaction to shift left in favor of the reactants. Q represents the reaction quotient at a certain point and by comparing it to K, you can predict how the reaction will proceed.
by Vicki Liu 2L
Tue Jan 14, 2020 1:34 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 5I.13
Replies: 3
Views: 39

Re: 5I.13

Adding on, the equilibrium constant can be used to find the numerical concentrations of reactants and products that make the system most stable. Essentially, it represents a fixed product to reactant ratio.
by Vicki Liu 2L
Tue Jan 14, 2020 1:30 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Change on Same Side
Replies: 6
Views: 64

Re: Change on Same Side

Yes, increasing N2 does affect H2 as well. To restore N2 to its equilibrium concentration, the reaction would shift to the right and favor product formation. As a result, more H2 would be used up and its concentration would decrease.
by Vicki Liu 2L
Tue Jan 14, 2020 1:28 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Why Ignore Liquid or Solid Volume When Calculating K
Replies: 7
Views: 65

Re: Why Ignore Liquid or Solid Volume When Calculating K

Kp is calculated using partial pressures not volume. Liquids and solids are excluded from the expression because they are available in excess so their pressures do not change before and after equilibrium.
by Vicki Liu 2L
Tue Jan 07, 2020 6:33 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium and Equilibrium Constant
Replies: 4
Views: 47

Re: Equilibrium and Equilibrium Constant

To my understanding, the equilibrium constant does not change— the ratio of products and reactants should always be the same at equilibrium. The only exception is that K will have a different value depending on the conditions (ex. temperature) that the reaction occurs under.
by Vicki Liu 2L
Tue Jan 07, 2020 6:26 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5.35 Part b
Replies: 2
Views: 40

Re: 5.35 Part b

I believe the pressure is given in kilopascals and dividing by 100 is to convert the units to bars (since 1 bar= 100 kPa).
by Vicki Liu 2L
Tue Jan 07, 2020 6:22 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Concentrations at Equilibrium
Replies: 6
Views: 95

Re: Concentrations at Equilibrium

At equilibrium, it’s not necessarily that the reactant and product concentrations are the same. Instead, the RATIO of reactant and product concentrations stays constant.
by Vicki Liu 2L
Tue Jan 07, 2020 5:52 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Homework 5J.1c
Replies: 3
Views: 48

Re: Homework 5J.1c

The reasoning behind the increase in H2 is that the reaction will shift to the right in order to return the amount of CO to its equilibrium concentration.
by Vicki Liu 2L
Tue Jan 07, 2020 5:49 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Q vs K
Replies: 13
Views: 153

Re: Q vs K

Another important thing to note is that by comparing the values of Q and K, you can predict how the reaction will proceed. If Q=K, the reaction has reached equilibrium. If Q<K, the reaction will form more products and if Q>K, more reactants.
by Vicki Liu 2L
Sat Dec 07, 2019 9:30 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone pairs location
Replies: 3
Views: 135

Re: Lone pairs location

To add on to the previous answer, the reason the lone pair should be placed on the equatorial plane is because this is what minimizes the repulsion between the lone pair and other outer atoms, which makes the molecule most stable.
by Vicki Liu 2L
Tue Dec 03, 2019 2:47 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ligand Charge
Replies: 1
Views: 20

Re: Ligand Charge

No, ligands can be neutral or negatively charged. An example is cyanide, or CN-.
by Vicki Liu 2L
Tue Dec 03, 2019 2:46 pm
Forum: Bond Lengths & Energies
Topic: Pi and Sigma Bonds and their affect on energy
Replies: 3
Views: 147

Re: Pi and Sigma Bonds and their affect on energy

Pi bonds cause the delocalization of electrons, which makes the overall molecule more stable and exist at a lower energy level.
by Vicki Liu 2L
Tue Dec 03, 2019 2:42 pm
Forum: Hybridization
Topic: Triple Bond Hybridization
Replies: 4
Views: 43

Re: Triple Bond Hybridization

When you're finding the hybridization, the focus should be on the number of regions of electron density not the bond order. With that said, a triple bond generally indicates sp hybridization because a triple bond generally means there are two regions of electron density for a completed octet.
by Vicki Liu 2L
Tue Dec 03, 2019 2:35 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Percentage Deprotonation
Replies: 2
Views: 23

Re: Percentage Deprotonation

Percentage deprotonation is just the ratio of the amount of a weak acid or base that has dissociated to the initial amount of the weak acid or base.
by Vicki Liu 2L
Tue Dec 03, 2019 2:30 pm
Forum: Hybridization
Topic: Conceptual meaning of hybridization
Replies: 3
Views: 45

Re: Conceptual meaning of hybridization

Hybridization explains how a carbon atom is able to form 4 covalent bonds. Looking at the orbital diagram for ground state carbon, its valence shell consists of a filled 2s orbital and 2 half-filled 2p orbitals. The only way carbon would be able to accommodate 4 shared electron pairs is by promoting...
by Vicki Liu 2L
Wed Nov 27, 2019 11:53 am
Forum: Ionic & Covalent Bonds
Topic: Dative Covalent Bonding
Replies: 4
Views: 141

Re: Dative Covalent Bonding

As touched on above, this type of interaction is responsible for the bonding of metal ions to ligands. The ligand provides the electron pair that is shared.
by Vicki Liu 2L
Wed Nov 27, 2019 11:45 am
Forum: Lewis Acids & Bases
Topic: Acid and Base Strength
Replies: 7
Views: 96

Re: Acid and Base Strength

Another indication of acid strength is how stable the resulting anion is. This can be determined by examining the electron pulling ability of the anion involved. From the example given in class, HClO is a stronger acid than HBrO, as the higher electronegativity of Cl stabilizes the negatively charge...
by Vicki Liu 2L
Wed Nov 27, 2019 11:26 am
Forum: Dipole Moments
Topic: Hydrogen Bonding Sites
Replies: 9
Views: 191

Re: Hydrogen Bonding Sites

As mentioned, hydrogen bonding sites are places on molecules where a hydrogen bond could be formed. So this could mean one of two things: a N, O, F atom with an available lone pair OR a H atom attached to a N, O, F atom. In the first instance, the lone pair could allow bonding with a nearby hydrogen...
by Vicki Liu 2L
Wed Nov 27, 2019 11:21 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Names of Common Ligands
Replies: 1
Views: 40

Re: Names of Common Ligands

There's a worksheet called "Naming Coordination Compounds" linked under the Course Materials section of the Chem 14A website with some ligands and their names. Hope this helps!
by Vicki Liu 2L
Wed Nov 27, 2019 11:16 am
Forum: Dipole Moments
Topic: Amide vs N-H
Replies: 2
Views: 122

Re: Amide vs N-H

When thinking about boiling points, the focus should be on intermolecular forces and not actual bonds. Boiling means breaking apart the molecules from each other, as in lowering their concentration into a gaseous phase. What you're referring to is the breaking apart of the molecule itself, which inv...
by Vicki Liu 2L
Thu Nov 21, 2019 8:36 pm
Forum: Hybridization
Topic: HW 2F.5.
Replies: 3
Views: 71

Re: HW 2F.5.

To find the hybridization, use the fact that the number of regions of electron density around the central atom corresponds to the number of hybridized orbitals. So draw out the Lewis structures for each molecule, count the number of bonding and lone pairs, and then write out the hybridization. For e...
by Vicki Liu 2L
Thu Nov 21, 2019 8:20 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Boiling Point Comparison
Replies: 1
Views: 55

Re: Boiling Point Comparison

Butanol would have a higher boiling point. This is because when you draw out the Lewis structures, you see that diethyl ether has London dispersion forces and dipole-dipole interactions. Butanol, on the other hand, has London dispersion forces and hydrogen bonding due to the O-H. Since hydrogen bond...
by Vicki Liu 2L
Thu Nov 21, 2019 8:14 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: 3F 15
Replies: 5
Views: 165

Re: 3F 15

In this case, the molecular weight comparison is not as important. Even though AsF5 has stronger London dispersion forces than AsF3, the dipole-dipole interactions that AsF3 has are much stronger than any London dispersion forces. In general, you only need to focus on London dispersion forces and co...
by Vicki Liu 2L
Thu Nov 21, 2019 1:36 pm
Forum: Electronegativity
Topic: Determining Polarity
Replies: 4
Views: 322

Re: Determining Polarity

To determine this, start by drawing the Lewis structure. When you do so, you’ll see that the central carbon atom has 4 bonding regions. Using VSEPR, this molecule would have a tetrahedral shape. Even though tetrahedral is a symmetrical molecular shape, drawing out the dipole moments (from partial po...
by Vicki Liu 2L
Thu Nov 21, 2019 1:30 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: dipole-dipole in a solid phase vs gas phase
Replies: 15
Views: 239

Re: dipole-dipole in a solid phase vs gas phase

Adding onto the previous answer, you can’t conclude that dipole-dipole interactions are stronger in the gas or solid phase. However, if you are given two samples of different polar molecules at the same temperature, if one of the samples is solid and one is gaseous, you can conclude that stronger di...
by Vicki Liu 2L
Wed Nov 13, 2019 11:05 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles Exceptions
Replies: 6
Views: 54

Re: Bond Angles Exceptions

Adding on to the previous answer, having different outer atoms would lead to slightly different bond angles due to the varying sizes of the atoms. So since Cl is larger than H, in CH3Cl, the bond angles would adjust to leave more space around the Cl atom and its lone pairs.
by Vicki Liu 2L
Wed Nov 13, 2019 10:53 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Problem 2E 7
Replies: 5
Views: 91

Re: Problem 2E 7

All the bond lengths are equal in SOCl2 because when you draw the ideal Lewis structure, you see that SOCl2 has resonance. This means that the bonds will all average out to the same length. Also, lone pairs don’t influence bond length, but they do influence bond angle.
by Vicki Liu 2L
Wed Nov 13, 2019 10:46 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: dipole moment clarification
Replies: 6
Views: 54

Re: dipole moment clarification

Adding on to the definition, polar molecules have bonds with dipole moments that do not cancel out to zero. In other words, they have a net dipole. Thus, polar molecules can be identified by drawing out dipole moments on a VSEPR model of the molecule.
by Vicki Liu 2L
Wed Nov 13, 2019 10:41 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR usage
Replies: 5
Views: 48

Re: VSEPR usage

To expand, certain molecular arrangements allow for more interactions with surrounding molecules. In other words, molecules that have a greater surface area, for example rod-shaped compared to spherical, allow for greater access and stronger intermolecular forces.
by Vicki Liu 2L
Wed Nov 13, 2019 9:22 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Methane VSEPR
Replies: 7
Views: 81

Re: Methane VSEPR

The 109.5 degree bond angles correspond to a tetrahedral structure. This is the molecular shape for CH4 and all other molecules with 4 bonding electron pair regions.
by Vicki Liu 2L
Thu Nov 07, 2019 4:38 pm
Forum: Lewis Structures
Topic: Favorable Bonds
Replies: 5
Views: 75

Re: Favorable Bonds

To expand on the first response, the reasoning behind why nitrogen atoms would want 3 bonds and oxygen atoms would want 2 is because this gets them to a formal charge of zero. If N has 3 bonds, it would need 1 lone pair to have a completed octet. So, formal charge = 5 - (2 + 6/2) = 0 If O has 2 bond...
by Vicki Liu 2L
Thu Nov 07, 2019 4:28 pm
Forum: Lewis Structures
Topic: Lewis Dot Structures
Replies: 4
Views: 53

Re: Lewis Dot Structures

I don't think you could arrange it so that there is only one dot on each side of the element shorthand. Since the octet rule should apply to Lewis structures (with some exceptions), there shouldn't be only those 4 electrons surrounding the atom. Other bonds would be connected to the atom and those 4...
by Vicki Liu 2L
Thu Nov 07, 2019 4:24 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Comparing forces of attraction
Replies: 4
Views: 50

Re: Comparing forces of attraction

Hydrogen bonds are actually a type of dipole dipole attraction. But out of dipole dipole attractions, they are the strongest. This is due to the high electronegativity difference between H atoms, which have very low electronegativity, and F, O, or N atoms, which have very high electronegativity.
by Vicki Liu 2L
Thu Nov 07, 2019 4:19 pm
Forum: Lewis Structures
Topic: 2.7 Lewis structure for N5 +
Replies: 3
Views: 55

Re: 2.7 Lewis structure for N5 +

The way I approached this problem was by first drawing 5 nitrogen atoms connected in a chain with single bonds. I then followed the octet rule and drew in electrons, noticing that 32 electrons would be needed if only single bonds were present. Comparing this to the 24 total valence electrons that N5...
by Vicki Liu 2L
Thu Nov 07, 2019 4:07 pm
Forum: Trends in The Periodic Table
Topic: Ionization energies
Replies: 3
Views: 58

Re: Ionization energies

Adding onto that, the extra electron in oxygen leads to additional electron-electron repulsion in the 2p orbital. This arises from the two electrons in the pair being in close proximity to one another, making it easier for one of them to be removed.
by Vicki Liu 2L
Thu Oct 31, 2019 4:45 pm
Forum: Properties of Light
Topic: atomic/molecular spectroscopy
Replies: 1
Views: 40

Re: atomic/molecular spectroscopy

I think one difference is that while atomic spectroscopy involves only electronic transitions, molecular spectroscopy involves electronic as well as vibrational and rotational transitions.
by Vicki Liu 2L
Thu Oct 31, 2019 4:40 pm
Forum: Lewis Structures
Topic: Hw 2B 5b
Replies: 1
Views: 30

Re: Hw 2B 5b

I think it might've just been a minor calculation error. Here's what I got:

NHF2
N: 5 valence electrons
H: 1 valence electron
F: 7 valence electrons * 2 = 14 valence electrons

Total = 5 + 1 + 14 = 20 valence electrons
by Vicki Liu 2L
Thu Oct 31, 2019 4:35 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Which orbital would contain the highest ionization energy?
Replies: 3
Views: 46

Re: Which orbital would contain the highest ionization energy?

You aren't necessarily wrong in that within each energy level, electrons in the s orbital would have the highest ionization energy. So for instance, within the energy level n=3, in order of increasing ionization energy, it would be 3d, 3p, 3s. However, it's probably better to think of it as electron...
by Vicki Liu 2L
Thu Oct 31, 2019 4:12 pm
Forum: Octet Exceptions
Topic: expanded valence shell confusion
Replies: 3
Views: 57

Re: expanded valence shell confusion

Expanded valence shells are an exception to the octet rule. So when drawing a Lewis structure, if the compound has extra valence electrons despite the outer atoms all being octets, the extra electrons can be added as lone pairs to the central atom, given it has a d-orbital available.
by Vicki Liu 2L
Thu Oct 31, 2019 3:39 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge
Replies: 5
Views: 60

Re: Formal Charge

Adding onto what has been said, the Lewis structure is most stable when formal charges are minimized but if there must be a formal charge, it should be a negative formal charge on the most electronegative atom.
by Vicki Liu 2L
Thu Oct 24, 2019 9:24 pm
Forum: DeBroglie Equation
Topic: hw problem 1B.23
Replies: 4
Views: 83

Re: hw problem 1B.23

It depends on the equation you're using because you want to make sure the unit for wavelength matches the units of other constants/values so that all the units cancel out nicely. In this case and most cases in general, wavelength should be changed to meters before being used in calculations.
by Vicki Liu 2L
Thu Oct 24, 2019 9:16 pm
Forum: Lewis Structures
Topic: Lewis Structures: Lone pairs as dots or lines?
Replies: 5
Views: 61

Re: Lewis Structures: Lone pairs as dots or lines?

I don't think you should use lines because in Lewis Structures, lines indicate covalent bonds, or shared electrons. It might be better to stick to using two dots to avoid confusion.
by Vicki Liu 2L
Thu Oct 24, 2019 9:09 pm
Forum: Bond Lengths & Energies
Topic: Bond Length and Bond Order
Replies: 1
Views: 37

Re: Bond Length and Bond Order

Yes, I believe your justification is correct. Single bonds are the longest, double bonds shorter, and triple bonds even shorter. This is because as the the strength of the bond increases, the atoms are pulled closer together.
by Vicki Liu 2L
Thu Oct 24, 2019 8:39 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Orbital Box Diagram
Replies: 5
Views: 63

Re: Orbital Box Diagram

An unpaired electron is generally drawn as an up arrow. I think this has to do with the fact that a spin up electron is at a lower energy level than a spin down electron, so it would fill the orbital box first.
by Vicki Liu 2L
Thu Oct 24, 2019 5:55 pm
Forum: Lewis Structures
Topic: Bond strength
Replies: 7
Views: 105

Re: Bond strength

To answer your second question, ionic and covalent bonds relate to electronegativity in that if the electronegativity difference is greater than 2.0, the bond is ionic. If it is less than 2.0, the bond is covalent. What this indicates in terms of strength is that in ionic bonds, the elements are muc...
by Vicki Liu 2L
Sat Oct 19, 2019 11:31 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 1D.26
Replies: 2
Views: 30

Re: 1D.26

For this question, use the rules for quantum numbers: n = an integer l = 0 to n-1 (where l= 0 means s, l= 1 means p, l= 2 means d, l= 3 means f, l= 4 means g) ml= -l to l ms= +1/2 or -1/2 Doing so, you see that... (a) cannot exist because l cannot equal 1 when n= 1 (b) can exist (c) I think the ques...
by Vicki Liu 2L
Sat Oct 19, 2019 11:21 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Stern and Gerlach Experiment
Replies: 1
Views: 18

Re: Stern and Gerlach Experiment

In the Stern and Gerlach experiment, they passed silver atoms through a magnetic field and observed how they were deflected. The results showed that the atoms would always end up in one of two positions, indicating that they had a quantized property. This property is called electron spin, and it cor...
by Vicki Liu 2L
Sat Oct 19, 2019 11:09 pm
Forum: Quantum Numbers and The H-Atom
Topic: 1D.13
Replies: 2
Views: 48

Re: 1D.13

To answer this problem, it'd probably be easiest to list out all the possible values for each question using the following rules: n = an integer l = 0 to n-1 m l = -l to l m s = +1/2 or -1/2 So, for instance, for part (a): n= 7, so l= 0, 1, 2, 3, 4, 5, 6 This is 7 different values so the answer for ...
by Vicki Liu 2L
Fri Oct 18, 2019 4:22 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Electron configuration with s and d subshells
Replies: 4
Views: 51

Re: Electron configuration with s and d subshells

Actually, I think it's the other way. According to the Aufbau principle, 4s orbitals are lower in energy than 3d orbitals, which explains why 4s is filled first. However, as the 3d orbital fills up, the relative energies of the two orbitals fluctuate and change. Eventually, 4s electrons become highe...
by Vicki Liu 2L
Fri Oct 18, 2019 4:09 pm
Forum: Quantum Numbers and The H-Atom
Topic: Quantum vs Classical
Replies: 5
Views: 98

Re: Quantum vs Classical

Classical mechanics generally pertains to larger objects, where events are more continuous and predictable. Quantum mechanics describes things on a smaller, particle level, where random transitions occur. For instance, classical mechanics describes light as a wave and quantum mechanics describes lig...
by Vicki Liu 2L
Sun Oct 13, 2019 4:53 pm
Forum: Properties of Light
Topic: P.E Experiment
Replies: 3
Views: 62

Re: P.E Experiment

Absorb means energy is being added to or gained by the system, while emit means energy is being lost or released by the system. In this case, I believe the answer is true, as the electron is going from a higher to lower energy level and energy is being lost.
by Vicki Liu 2L
Sun Oct 13, 2019 4:48 pm
Forum: Properties of Light
Topic: Wave-Particle Behavior
Replies: 4
Views: 77

Re: Wave-Particle Behavior

The photoelectric effect supports the particle behavior view, as it suggests that each photon interacts with each electron. On the other hand, an observation that supports the wave view is that diffraction patterns result from electrons being passed through a crystal, the same way they do when light...
by Vicki Liu 2L
Sun Oct 13, 2019 4:40 pm
Forum: Properties of Electrons
Topic: electron energy levels
Replies: 6
Views: 61

Re: electron energy levels

Both are similar in that they detect electron movement as a response to light. However, the photoelectric effect has to do with electrons actually being emitted, meaning photons have to be at a sufficient energy level. Atomic spectroscopy on the other hand can observe in-between states.
by Vicki Liu 2L
Sun Oct 13, 2019 4:24 pm
Forum: Properties of Electrons
Topic: Photons
Replies: 5
Views: 60

Re: Photons

A photon is a particle of light that carries energy, so that value must be positive. However, the energy change caused by a photon can be either positive or negative, depending on whether a photon is absorbed (positive energy change) or emitted (negative energy change).
by Vicki Liu 2L
Sun Oct 13, 2019 4:03 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: atomic spectra
Replies: 5
Views: 91

Re: atomic spectra

Atomic spectra refers to the series of colored lines formed by electrons emitting different wavelengths of light.
by Vicki Liu 2L
Thu Oct 03, 2019 12:24 pm
Forum: Limiting Reactant Calculations
Topic: Fundamentals M7
Replies: 3
Views: 60

Re: Fundamentals M7

Another way of approaching limiting reactant problems is by taking the amount of each reactant in grams and converting it to moles. Afterwards, compare the ratio of moles present:moles required for each reactant. Whichever one has the lower ratio is the limiting reactant. So in this case, 125 kg of ...
by Vicki Liu 2L
Thu Oct 03, 2019 11:58 am
Forum: Empirical & Molecular Formulas
Topic: Homework L39
Replies: 5
Views: 76

Re: Homework L39

Tin is an element that exists in more than one oxidation state, meaning its ions could carry different charges. For tin specifically, it could be Sn2+or Sn4+. But since oxygen's oxidation number is -2 and there are two oxygen ions present in SnO2, for the net charge to equal 0, the tin ion must carr...
by Vicki Liu 2L
Thu Oct 03, 2019 11:44 am
Forum: Balancing Chemical Reactions
Topic: Question E3
Replies: 3
Views: 85

Re: Question E3

Since the given molar mass of astatine is exactly 3 times that of gallium, you could then draw the conclusion that there would have to be 1 astatine atom for every 3 gallium atoms. By looking at the diagram and counting, there are 9 gallium atoms on the left. Therefore, there would have to be 3 asta...
by Vicki Liu 2L
Wed Oct 02, 2019 5:15 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: HW Problem E17
Replies: 5
Views: 79

Re: HW Problem E17

Also, by the way, in the last sentence, instead of "molarity" I think it should be "molar mass". Molarity refers to the concentration of a solution in mol/L. No big deal but just something to look out for!

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