## Search found 184 matches

Mon Mar 16, 2020 2:31 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kw and other constants
Replies: 9
Views: 215

### Re: Kw and other constants

Kw is the equilibrium constant for water, and it is always equal to 1 * 10^-14. This can only be applied for conjugate acid-base pairs because the concentration of H+ and OH- the two produces are tied together. If one goes up, the other goes down, thus the conjugate seesaw.
Sun Mar 15, 2020 2:37 pm
Forum: Administrative Questions and Class Announcements
Topic: Athena
Replies: 34
Views: 2150

### Re: Athena

While I may not share the same love for Athena as you do, I love Greek mythology so thank you for sharing this special piece.
Thank you for everything Dr Lavelle! I hope these past two quarters have been worth your time. Please take care, stay safe, and have a good break!
Sat Mar 14, 2020 8:56 pm
Forum: Calculating Work of Expansion
Topic: Mnemonic for State Functions
Replies: 3
Views: 101

### Mnemonic for State Functions

Does anyone remember what was the mnemonic Lyndon taught us for the state functions PDTVHUGS?
Sat Mar 14, 2020 6:51 pm
Forum: Administrative Questions and Class Announcements
Topic: Tuesday Test 2 Answer Key
Replies: 4
Views: 115

### Re: Tuesday Test 2 Answer Key

KeyaV1C wrote:I don’t think it is. I saw the Thursday one floating around here but not the Tuesday one. Did you have any specific questions on the Tuesday test?

I wanted to know the answer for Question 4
Sat Mar 14, 2020 12:12 pm
Forum: Administrative Questions and Class Announcements
Topic: Tuesday Test 2 Answer Key
Replies: 4
Views: 115

### Tuesday Test 2 Answer Key

Does anyone know if the answer key for the test 2 given during Tuesday discussion sessions are posted anywhere?
Fri Mar 13, 2020 10:28 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Homework 7.23
Replies: 1
Views: 43

### Homework 7.23

(a) What is the overall reaction for the following mechanism? ClO- + H2O ⇌ HClO + OH- (fast equil) HClO + I- ⇌ HIO + Cl- (very slow) HIO + OH- ⇌ IO- + H2O (fast equil) (b) Write the rate law based on this mechanism. (c) How will the reaction rate depend on the pH of the solution? (d) How would the r...
Fri Mar 13, 2020 9:51 am
Forum: Administrative Questions and Class Announcements
Topic: W20, Week 10 Discussion 2F, 2I, 2L
Replies: 10
Views: 3698

### Re: W20, Week 10 Discussion 2F, 2I, 2L

Hiba Alnajjar_2C wrote:

Will the answer key for Tuesday's test be posted as well? Thank you!

Wondering the same thing!
Thu Mar 12, 2020 10:28 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Homework 7E3
Replies: 2
Views: 55

### Homework 7E3

The presence of a catalyst provides a reaction pathway in which the activation energy of a certain reaction is reduced from 125 kJ/mol−1 to 75 kJ/mol−1. (a) By what factor does the rate of the reaction increase at 298 K, all other factors being equal? (b) By what factor would the rate change if the ...
Thu Mar 12, 2020 10:16 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Homework 7E1
Replies: 4
Views: 77

### Homework 7E1

How does a catalyst affect (a) the rate of the reverse reaction; (b) the value of ∆Hr° for the reaction?

Can someone explain the answer for part B?
Thu Mar 12, 2020 9:08 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activation Energy vs Free Energy of Activation
Replies: 6
Views: 160

### Activation Energy vs Free Energy of Activation

This is from Outline 6: Understand the difference between activation energy and free energy of activation.
Can someone explain their differences?
Thu Mar 12, 2020 7:03 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Activated Complex vs Transition State
Replies: 5
Views: 146

### Activated Complex vs Transition State

What's the difference between activated complex and transition state in the transition-state theory?
Thu Mar 12, 2020 7:01 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Collision Frequency
Replies: 3
Views: 61

### Re: Collision Frequency

MingdaH 3B wrote:I think we do need to understand it since I remember Lavelle talking about it in lecture.

He did? Along with its equation??
Thu Mar 12, 2020 2:33 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Collision Frequency
Replies: 3
Views: 61

### Collision Frequency

Do we need to know what collision frequency is for collision theory?
Wed Mar 11, 2020 12:12 am
Forum: Administrative Questions and Class Announcements
Topic: Saying Thank You to Lyndon and the Fellow UAs
Replies: 2
Views: 96

### Saying Thank You to Lyndon and the Fellow UAs

Since there's a post for saying thank you to Dr Lavelle, I felt like there needs to be a post dedicated to Lyndon and the other UAs. Due to the sudden cancellation of all in-person classes and gatherings, it seems like we can't properly express our gratuity to Lyndon (and of course the other UAs as ...
Wed Mar 11, 2020 12:06 am
Forum: Administrative Questions and Class Announcements
Topic: Saying Thank You to Dr. Lavelle
Replies: 416
Views: 143021

### Re: Saying Thank You to Dr. Lavelle

To Dr Lavelle, Due to the unexpected circumstances, it seems that we cannot properly say goodbye to you tomorrow. But I really want to take this time to say a big THANK YOU for the past two quarters. Chemistry has always been a subject that I've dreaded (due to bad prior experiences)-- and honestly,...
Thu Mar 05, 2020 12:26 am
Forum: General Rate Laws
Topic: Lecture Question
Replies: 3
Views: 137

### Lecture Question

In lecture today, the slide mentioned something about how the rate law and integrated considers the reactant only and that "therefore the product must be in a different phase or remove product". What does that mean?
Wed Mar 04, 2020 11:45 pm
Forum: Zero Order Reactions
Topic: Rate of Reaction Independent of [A]o
Replies: 3
Views: 76

### Rate of Reaction Independent of [A]o

I know Dr Lavelle explained this a bit in lecture but I don't remember all too much about it. How does a catalyst/enzyme cause the reaction rate to be independent of the initial concentration of the reactant?
Mon Mar 02, 2020 3:01 am
Forum: Student Social/Study Group
Topic: Test 2 Homework Problems, Etc
Replies: 6
Views: 129

### Test 2 Homework Problems, Etc

Am I the only one being utterly confused about the homework problems? The examples in class and in the textbook for section 6L doesn't even compare to the exercise problems. It's like what we learn from lecture and the textbook have a huge difference in the homework problems we are asked to solve an...
Mon Mar 02, 2020 2:56 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Homework 6L.9
Replies: 4
Views: 92

### Re: Homework 6L.9

So if we start off with an equation: 2KMnO4 + 8FeCl2 --> 2KCl + 2MnCl2 + 8FeO + 5Cl2. Through this equation you would see that your potassium value doesn't change, its charge is still +1. You also notice that the charge of Cl doesn't change and that it is still -1. That means MnO4 and Fe are your c...
Mon Mar 02, 2020 2:53 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.7 C
Replies: 2
Views: 68

### Re: 6L.7 C

Cd(OH)2(s)+2e- →Cd(s)+2OH^-(aq) E°(anode)=-0.81V Ni(OH)3(s)+e-→ Ni(OH)2(s)+OH^-(aq) E°(cathode)=+0.49V Reversing the anode rxn and multiplying the cathode rxn by 2 yields Cd(s)+2OH^-(aq)→Cd(OH)2(s)+2e- 2Ni(OH)3+2e-→2Ni(OH)2(s)+2OH^-(aq) then, upon addition, 2Ni(OH)2(s)+Cd(s)→Cd(OH)2(s)+2Ni(OH)2(s) ...
Mon Mar 02, 2020 1:55 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Homework 6L.5 Part B and C
Replies: 1
Views: 61

### Homework 6L.5 Part B and C

For Part B "Ce4+(aq) + I-(aq) -> I2(s) + Ce3+(aq)", why is there a Pt(s) on the side of the anode as well? Isn't only the electrode on the cathode side made of platinum? In the solutions manual, it says an inert electrode is needed when both oxidized and reducing species are in the same so...
Mon Mar 02, 2020 1:43 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Stoichiometric Coefficients in Cell Diagrams
Replies: 3
Views: 67

### Stoichiometric Coefficients in Cell Diagrams

Do we not input stoichiometric coefficients in cell diagrams?
Mon Mar 02, 2020 1:17 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.3
Replies: 2
Views: 36

### 6L.3

For Part D "(d) Pt(s)|O2(g)|H1(aq)||OH2(aq)|O2(g)|Pt(s)", the balanced equation for the cell reaction is H20(l) -> H+(aq) + OH-(aq) and Ecell°= -0.83V. Can someone explain why the solution manual says "Note: This balanced equation corresponds to the cell notation given. The spontaneou...
Mon Mar 02, 2020 1:04 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6L.3d homework question
Replies: 3
Views: 82

### Re: 6L.3d homework question

The right side of the electrode is for reduction and the left side of the electrode is for oxidation so the half reactions are Oxidation (at anode): 2H2O —> O2 + 4H^(+) + 4e- Reduction (at cathode): O2 + 2H2O + 4e- —> 4OH- How do we know the oxidation reaction is H20 oxidizing to O2 and 4H+ when on...
Sun Mar 01, 2020 11:40 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Textbook Example
Replies: 1
Views: 14

### Textbook Example

Can someone explain where the Cl- came from in Step 1 and where the H+ came from in Step 2? Aren't cell diagrams supposed to depict all reactants and products in the reaction?
Sun Mar 01, 2020 11:14 am
Forum: Balancing Redox Reactions
Topic: 6K3 Help
Replies: 1
Views: 45

### 6K3 Help

(a) Reaction of thiosulfate ion with chlorine gas: Cl2(g) + (S2O3)^2- (aq) -> Cl2(aq) + (SO4)2- (aq) Can someone explain how the balanced oxidation reaction (S2O3)^2- (aq) + 5H20 (l) -> 2(SO4)2- (aq) + 10H+ (aq) + 8e- shows the change of oxidation number of sulfur that corresponds to the 8e-? I'm tr...
Sun Mar 01, 2020 2:22 am
Forum: Balancing Redox Reactions
Topic: Oxidation State/Number in General
Replies: 2
Views: 57

### Oxidation State/Number in General

I understand that the oxidation number/state is the charge of an element. But what I don't understand is how certain elements can have so many different oxidation numbers, i.e. carbon, while others have so less, i.e. oxygen and hydrogen? For example, homework problem 6K1 "The following redox re...
Sun Mar 01, 2020 2:08 am
Forum: Balancing Redox Reactions
Topic: Redox Reactions and Acid/Base Reactions
Replies: 9
Views: 209

### Redox Reactions and Acid/Base Reactions

Are all redox reactions either an acid reaction or base reaction? If not, what are some examples of redox reactions that aren't acid/base reactions?
Sun Mar 01, 2020 2:02 am
Forum: Balancing Redox Reactions
Topic: Textbook Example
Replies: 1
Views: 38

### Textbook Example

Can someone explain why the two hydrogens have a +1 charge each? Don't hydrogens have a neutral charge unless it's a H+ proton?
Sun Mar 01, 2020 12:21 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Outline 4 Learning Objective
Replies: 2
Views: 57

### Outline 4 Learning Objective

Understand why reaction free energy depends on pressure and the equilibrium constant.
Can someone explain why G depends on pressure?
Sat Feb 29, 2020 11:26 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: ∆G and ∆G°
Replies: 7
Views: 184

### ∆G and ∆G°

I know that if ∆G° is negative, that means the reaction is spontaneous (since K>1 and products are favored at equilibrium) and if ∆G° is positive, the reaction is not spontaneous. Does this apply for ∆G as well?
Sat Feb 29, 2020 6:43 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Solving Gibbs Free Energy Problems
Replies: 1
Views: 55

### Solving Gibbs Free Energy Problems

For questions like 5G.15, (a) Calculate the reaction Gibbs free energy of N2(g) + 3 H2(g) -> 2 NH3(g) when the partial pressures of N2, H2, and NH3 are 4.2 bar, 1.8 bar, and 21 bar, respectively, and the temperature is 400. K. For this reaction, K = 41 at 400. K. (b) Indicate whether this reaction m...
Wed Feb 26, 2020 11:06 am
Forum: Administrative Questions and Class Announcements
Topic: Monday 2/24 Lecture
Replies: 1
Views: 86

### Monday 2/24 Lecture

Hi,
Would someone please be kind enough to share their notes from Monday's lecture? I had to leave early so I missed like the last two slides of notes :(
Mon Feb 24, 2020 10:27 pm
Forum: Balancing Redox Reactions
Topic: 6K1
Replies: 3
Views: 84

### 6K1

This is probably one of the easiest redox questions but I don't understand redox overall (with the balancing, half-rxns, etc) :( can someone explain how to do this? The following redox reaction is used in acidic solution in the Breathalyzer test to determine the level of alcohol in blood: H1 (aq) + ...
Mon Feb 24, 2020 2:16 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: No Conducting Solids
Replies: 1
Views: 47

### No Conducting Solids

In lecture, there was a slide about half-reactions having no conducting solids and the reaction was 2Fe^3+(aq) + Cu(s) -> Cu^2+(aq) + 2Fe^2+(aq).
What does it mean there are no conducting solids? Is the Cu(s) not a conducting solid?
Tue Feb 18, 2020 12:09 pm
Forum: Van't Hoff Equation
Topic: ∆H and ∆S not temperature dependent
Replies: 2
Views: 83

### ∆H and ∆S not temperature dependent

In lecutre, Professor Lavelle said, when we use the Van't Hoff equation to calculate K at two different temperatures, the ∆H and ∆S don't have any subscripts because enthalpy and entropy aren't temperature dependent. How do we know they aren't temperature dependent? What is the reasoning behind that...
Mon Feb 17, 2020 6:39 pm
Forum: Administrative Questions and Class Announcements
Topic: Is this course curved?
Replies: 7
Views: 223

### Is this course curved?

Does anyone know if the midterm/final/course overall is curved?
Mon Feb 17, 2020 6:25 pm
Forum: Administrative Questions and Class Announcements
Topic: 14BL and 14C
Replies: 8
Views: 163

### Re: 14BL and 14C

I don't know about 14C but I'm taking 14BL currently with 14B and the workload of 14BL seems decent at the moment. I don't think there should be a problem taking 14C and 14BL. You will just need to retain mainly acid-base concepts for 14BL because it focuses on that a lot.
Tue Feb 11, 2020 10:53 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Homework 4J.7
Replies: 1
Views: 46

### Homework 4J.7

Calculate the standard reaction entropy, enthalpy, and Gibbs free energy for each of the following reactions from data in Appendix 2A: (a) the decomposition of hydrogen peroxide: 2 H2O2(l) -> 2 H2O(l) + O2(g) (b) the preparation of hydrofluoric acid from fluorine and water: 2 F2(g) + 2 H2O(l) -> 4 H...
Mon Feb 10, 2020 12:31 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Stability and Bond Enthalpy
Replies: 3
Views: 39

### Stability and Bond Enthalpy

Do higher bond enthalpies indicate higher stability?
Mon Feb 10, 2020 11:41 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Difference between ΔH, ΔH°, ΔH(rxn)°, and ΔH(f)°
Replies: 2
Views: 58

### Difference between ΔH, ΔH°, ΔH(rxn)°, and ΔH(f)°

Can someone explain the difference between all these notations: ΔH, ΔH°, ΔH(rxn)°, and ΔH(f)°? I feel like some questions refer to ΔH°as the same as ΔH(rxn)°but some don't so I'm utterly confused. It would also help if you explain this with the units correlating to each because I know some has "...
Mon Feb 10, 2020 11:34 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.23 homework help
Replies: 4
Views: 50

### Re: 4D.23 homework help

Why does the solution manual (6th edition) put "The reaction we want is N2 (g) + 5/2 O2 (g) -> N2O5 (g)" when there's no N2 in the reactions given? Shouldn't we create a reaction that does include the reactants and products of the 2 reactions given, which will be 2NO (g) + 3/2 O2 (g) -> N2...
Mon Feb 10, 2020 1:23 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy Definition
Replies: 2
Views: 31

### Enthalpy Definition

When we talk about enthalpy in any aspect (standard rxn enthalpy, standard enthalpy formation, change in enthalpy, etc), is it always defined as the amount of heat released or absorbed at constant pressure?
Sun Feb 09, 2020 10:14 pm
Forum: Phase Changes & Related Calculations
Topic: Homework 4C 13
Replies: 7
Views: 110

### Re: Homework 4C 13

Emma Popescu 1L wrote:For this question, why do we use the specific heat capacity of liquid water instead of ice?

we use the specific heat capacity of liquid water for ice because we're calculating the heat after it has been melted from solid to liquid
Sun Feb 09, 2020 9:35 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Homework 4C3
Replies: 2
Views: 44

### Re: Homework 4C3

for parts a and b, you would use similar processes. for part a, you would use the equation q=nCpdeltaT, and for part b, the equation q=nCvdeltaT. These are pretty much the same equations, just one is for constant pressure, whereas the other one is for constant volume. Plug in the values in each equ...
Sun Feb 09, 2020 6:38 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Homework 4C3
Replies: 2
Views: 44

### Homework 4C3

Calculate the final temperature and the change in enthalpy when 765 J of energy is transferred as heat to 0.820 mol Kr(g) at 298 K and 1.00 atm (a) at constant pressure; (b) at constant volume. Treat the gas as ideal.

Can someone run through the steps on how to solve this problem?
Sun Feb 09, 2020 6:31 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy Formula
Replies: 2
Views: 58

### Enthalpy Formula

In lecture, we went over 3 methods to calculate enthalpy as well as ΔH = H(products) - H(reactants). In the textbook, they have the formula ΔH = ΔU + PΔV. Are we not allowed to use this formula (alongside ΔU = q + w) to calculate the change in enthalpy?
Sun Feb 09, 2020 1:44 am
Forum: Student Social/Study Group
Topic: Any Worksheets from UA/TA/etc?
Replies: 14
Views: 308

### Re: Any Worksheets from UA/TA/etc?

Celena Kim 2I wrote:If you search up "worksheet," you can find a few! I believe Hannah just posted one recently from her session.

I tried searching but I don't find anything?
Sun Feb 09, 2020 1:43 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Equipartition Therom
Replies: 3
Views: 46

### Equipartition Therom

Do we need to know the concepts in Topic 4B3? I don't remember Dr. Lavelle mentioning any of those terms in lecture.
Sun Feb 09, 2020 12:17 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Internal Energy as State Function
Replies: 1
Views: 52

### Internal Energy as State Function

I know that the purpose of this image is to show that internal energy is a state function because the internal energy of both are the same, just that the path taken is different. However, what I'm wondering is how the volume of b expanded if there's no work done and no heat input.
Sat Feb 08, 2020 11:42 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Homework 4A13
Replies: 5
Views: 114

### Homework 4A13

A constant-volume calorimeter was calibrated by carrying out a reaction known to release 3.50 kJ of heat in 0.200 L of solu- tion in the calorimeter (q 5 23.50 kJ), resulting in a temperature rise of 7.32 8C. In a subsequent experiment, 100.0 mL of 0.200 m HBr(aq) and 100.0 mL of 0.200 m KOH(aq) wer...
Sat Feb 08, 2020 11:09 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Homework 4A7
Replies: 2
Views: 43

### Homework 4A7

For part a of this problem: (a) Calculate the heat that must be supplied to a copper kettle of mass 400.0 g containing 300.0 g of water to raise its tem- perature from 20.0 8C to the boiling point of water, 100.0 8C. (b) What percentage of the heat is used to raise the temperature of the water? why ...
Sat Feb 08, 2020 3:58 pm
Forum: Calculating Work of Expansion
Topic: Reversible Process and Work
Replies: 4
Views: 53

### Reversible Process and Work

Can someone give a dumb downed explanation of how reversible processes generate maximum work?
Sun Feb 02, 2020 11:00 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: H and q
Replies: 7
Views: 79

### Re: H and q

q equals delta H when pressure is constant
Sun Feb 02, 2020 11:00 am
Forum: Student Social/Study Group
Topic: Midterm Topics
Replies: 12
Views: 208

### Midterm Topics

Does anyone know up to which outline the midterm will be covering?
Sun Feb 02, 2020 10:58 am
Forum: Phase Changes & Related Calculations
Topic: Calorimeter
Replies: 8
Views: 158

### Re: Calorimeter

Bomb calorimeter is just a specific type of calorimeter. It works best when trying to keep volume and moles of the gas constant bc it's perfectly sealed and isolated.
Sun Feb 02, 2020 10:57 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: When to leave out reactants/products from enthalpy calculations
Replies: 4
Views: 50

### Re: When to leave out reactants/products from enthalpy calculations

I believe Dr Lavelle gave a list of gases that are in the purest form (O2, N2, etc). I think there should be a list in the textbook.
Sun Feb 02, 2020 10:55 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 3 Methods
Replies: 3
Views: 55

### 3 Methods

Can someone explain how and when the three methods should be the used?
Sun Feb 02, 2020 10:49 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Work done by expansion
Replies: 8
Views: 64

### Re: Work done by expansion

Wouldn't that be the work integral equation? Dr Lavelle didn't go through how to solve problems with it but he did show the equation
Sun Jan 26, 2020 8:11 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Method 2
Replies: 4
Views: 42

### Re: Method 2

I don't have my notebook with me currently but if I remember correctly, Method 2 was adding the bond energies of every bond in the molecule before and after the reaction and subtracted them from each other. And whether the result is positive or negative, it would indicate that the reaction is endoth...
Sun Jan 26, 2020 8:07 pm
Forum: Phase Changes & Related Calculations
Topic: Heat vs temperature
Replies: 6
Views: 105

### Re: Heat vs temperature

To change something from one phase to another, say, solid to liquid, heat is needed. This can be easily seen in any real-life example (ice becoming water due to heat). What the slide means from "temperature staying constant" means that the process of adding heat is slow so the temperature ...
Sun Jan 26, 2020 8:05 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: percent ionization
Replies: 5
Views: 56

### Re: percent ionization

a small percentage indicates that a very very minute amount of reactant had donated a proton; a very very minute amount could mean 0.00000001, and from ICE boxes, subtracting that very small value by, say, 0.1, would make essentially no difference. So approximating 0.1-x to 0.1 is perfectly fine
Sun Jan 26, 2020 8:02 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy is said to be additive
Replies: 10
Views: 122

### Re: Enthalpy is said to be additive

it basically means the delta H values can be added together (even if it's a negative number, which will just make the addition into a subtraction)
Sun Jan 26, 2020 8:00 pm
Forum: Administrative Questions and Class Announcements
Topic: Fall Quarter Final?
Replies: 12
Views: 294

### Re: Fall Quarter Final?

:o we can pick up our exam?
Sun Jan 26, 2020 7:59 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: solvent
Replies: 10
Views: 87

### Re: solvent

If I'm not wrong, in the scopes of our class, solvents tend to be H2O (l) and will probably only be water.
Mon Jan 20, 2020 10:04 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: homework problem 6D.3
Replies: 2
Views: 43

### Re: homework problem 6D.3

I wondered the same thing. I just thought the solutions manual to be wrong and wrote the equation as HClO2 + H2O ⇌ ClO2 + H3O+ After this, I calculated the concentration of H3O+ from the pH value. Now I'm trying to solve for the Ka but I was wondering, is 0.10 M of HClO the equilibrium concentration...
Mon Jan 20, 2020 2:25 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: ka/kb and pH/pOH relationship
Replies: 1
Views: 87

### ka/kb and pH/pOH relationship

If NH3 + H20 -> NH4+ + OH- has a certain kb value that is related to the concentration of OH- in the solution, is the ka of that reaction related to the concentration of H3O+ in that same solution? If so, wouldn't that make ka and kb the same as pH and pOH, especially since ka * kb = kw and pH + pOH...
Mon Jan 20, 2020 2:07 pm
Forum: Student Social/Study Group
Topic: Any Worksheets from UA/TA/etc?
Replies: 14
Views: 308

### Any Worksheets from UA/TA/etc?

Does anyone know if there are any practice worksheets from UAs, TAs, etc for Chem 14B? I remember for Chem 14A last quarter, some UAs had worksheets posted on here so I'm just wondering if there is any for this course.
Mon Jan 20, 2020 2:01 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH and pOH in Reactions
Replies: 3
Views: 117

### pH and pOH in Reactions

Please correct my understanding if I'm wrong: in, say, a weak base reaction like NH3 + H20 ⇌ NH4+ + OH-, there are still H30 molecules in the reaction (to maintain autoprotolysis equilibrium Kw), but H30 is just not explicitly written. Am I correct? Reasoning: we can always calculate the pH from the...
Mon Jan 20, 2020 1:28 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 6B.11
Replies: 2
Views: 105

### Re: 6B.11

Yes, Na2O (s) + H2O (l) ⇌ 2Na+ (aq) + 2OH- (aq) is the correct reaction If I broke that reaction into two composite ones, would they be 1) Na2O (s) + H2O (l) -> 2NaOH (aq) and 2) 2NaOH (aq) -> 2Na+ (aq) + 2OH- (aq) ? If so, why doesn't the 2nd reaction not have H20 in the reaction? I tried to write...
Mon Jan 20, 2020 2:38 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 6B.11
Replies: 2
Views: 105

### 6B.11

Hello, Can someone write out the reaction equation for this problem? I just want to make sure I'm understanding it. "A student added solid Na2O to a volumetric flask of volume 200.0 mL, which was then filled with water, resulting in 200.0 mL of NaOH solution. Then 5.00 mL of the solution was tr...
Sun Jan 19, 2020 3:12 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Exothermic and Endothermic Reactions
Replies: 5
Views: 87

### Exothermic and Endothermic Reactions

Are all reactions exothermic or endothermic, whether slightly or strongly exo/endothermic? And on this topic, are all reactions with a positive delta H going to be endothermic and all reactions with a negative delta H going to be exothermic, despite forming or breaking bonds during the reaction?
Sun Jan 19, 2020 3:10 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Effect of Temperature on K
Replies: 2
Views: 34

### Effect of Temperature on K

How come changing temperature permanently changes K and not just Q, like the effect of other (adding reactant/products, etc) changes? Since K, the equilibrium constant, is a constant, wouldn't temperature just affect Q like the others?
Sun Jan 19, 2020 3:04 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Test 1 Acids and Bases Topic
Replies: 9
Views: 152

### Test 1 Acids and Bases Topic

I struggled to understand acids and bases a lot for Chem 14A so can anyone give me a small run-down of what they are, how to tell which is which, and how to understand salt reactions? Also, how much about acids and bases in general do we need to know in order to do pH, pOH, Kw, Ka, and Kb calculatio...
Sun Jan 19, 2020 3:02 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: autoprotolysis
Replies: 5
Views: 57

### Re: autoprotolysis

Karina Kong 2H wrote:Could someone explain how autoprotolysis of water leads to Kw?

need help on this too; also, does anyone know how much we need to know about the topic of autoprotolysis for the test?
Sun Jan 19, 2020 12:10 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Questions and Sig Figs
Replies: 6
Views: 71

### Re: Equilibrium Questions and Sig Figs

I agree with the last user's post in that it is best to round to the number of given sig figs at the very end. When dealing with pH however, the sig figs are typically calculated differently (calculated in the way of a logarithm) which I believe is 3 sig figs usually. For pH, the sig figs in the gi...
Sat Jan 18, 2020 6:08 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Questions and Sig Figs
Replies: 6
Views: 71

### Equilibrium Questions and Sig Figs

I know that Dr Lavelle always ask us to try and keep as many digits as possible when doing multi-step problems but do we do the same for equilibrium questions (with ICE box and such)? For example, after calculating x (through quadratic or whatever necessary algebra), should we round to proper sig fi...
Thu Jan 16, 2020 12:06 pm
Forum: Student Social/Study Group
Topic: Week 1 Discussion
Replies: 1
Views: 113

### Week 1 Discussion

Can anyone in Dis Sec 2A, 2C, 2J share their notes from Week 1's discussion section?
Thu Jan 16, 2020 1:00 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Endothermic/Exothermic Rxns and Delta H
Replies: 3
Views: 119

### Endothermic/Exothermic Rxns and Delta H

For question like Module 4 Q17: Determine the shift in equilibrium, if any, which will occur for the following reactions when the temperature is increased a) Photosynthesis: 6 CO2 (g) + 6 H2O (l) ⇌ C6H12O6(s) + 6 O2 (g) delta H° = +2802 kJ.mol-1 b) The hydrolysis of ATP: ATP (aq) + H2O (l) ⇌ ADP + P...
Thu Jan 16, 2020 12:36 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Module 4 Q15
Replies: 2
Views: 32

### Module 4 Q15

The photosynthesis reaction, 6 CO2(g) + 6 H2O(l) ⇌ C6H12O6(aq) + 6 O2(g), is endothermic. What effect will the following changes have on the equilibrium composition. a) Water is added. b) The partial pressure of CO2 is decreased. A. a) Decrease [C6H12O6] and [O2], b) Decrease [O2] B. a) Decrease [C6...
Wed Jan 15, 2020 2:41 pm
Forum: Student Social/Study Group
Topic: Discussion Sec 2A, 2C, 2J
Replies: 2
Views: 89

### Re: Discussion Sec 2A, 2C, 2J

Ronak Naik wrote:I attached a picture of my notes.

You're awesome! Do you by chance have notes from the Week 1 discussion?
Wed Jan 15, 2020 1:21 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Module 4 Q2
Replies: 2
Views: 51

### Module 4 Q2

State whether the equilibrium shifts towards products, reactants, or neither when the given change occurs. 2 HI(g) + Cl2(g) ⇌ 2 HCl(g) + I2(s) delta H° = -238.0 kJ.mol-1 i. The volume of the system is compressed. ii. The temperature of the system is decreased. For part i, using the quick way, we kno...
Wed Jan 15, 2020 1:09 am
Forum: Student Social/Study Group
Topic: Discussion Sec 2A, 2C, 2J
Replies: 2
Views: 89

### Discussion Sec 2A, 2C, 2J

Hello!
To anyone in Discussion Sec 2A, 2C, or 2J, can you share the notes from Week 1 discussion?
Tue Jan 14, 2020 12:26 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Significant Figures
Replies: 1
Views: 39

### Significant Figures

For question 5I.19 "A reaction mixture that consisted of 0.400 mol H2 and 1.60 mol I2 was introduced into a flask of volume 3.00 L and heated. At equilibrium, 60.0% of the hydrogen gas had reacted. What is the equilibrium constant K for the reaction H2(g) 1 I2(g) ⇌ 2 HI(g) at this temperature?&...
Sun Jan 12, 2020 6:41 pm
Forum: Ideal Gases
Topic: P=(n/v)RT
Replies: 12
Views: 160

### Re: P=(n/v)RT

V is also divided by PRT :) it's just typed (n/V)RT for it be easily seen as concentration * RT. (nRT)/V means the same thing
Sun Jan 12, 2020 3:47 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Rounding in K problems
Replies: 4
Views: 45

### Re: Rounding in K problems

I don't know why they were rounded before plugging in. But the general rule for tests, midterm, and final is to keep as many digits as possible (in multi-step problems) for each calculation and at the end when you have a final answer, go according to the least number of sig figs in the problem.
Sun Jan 12, 2020 3:34 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Temperature and K
Replies: 6
Views: 103

### Re: Temperature and K

K changes with temperature because there are endothermic or exothermic reactions. These reactions are affected by temperature changes (increase heat or decrease heat) and the concentrations of the reactants or products (depending on which one is affected) are permanently changed, thus the K value ch...
Sun Jan 12, 2020 12:45 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: ICE vs Normal Concentrations
Replies: 5
Views: 38

### Re: ICE vs Normal Concentrations

First off, what do you mean by "regular equilibrium conventrations"? And second, I think ICE boxes can be used for any equilibrium question if there is a change in the equilibrium concentration (from an initial amount to a final amount). ICE boxes make those kind of questions more organize...
Sun Jan 12, 2020 12:43 pm
Forum: Ideal Gases
Topic: Bars vs atmospheres
Replies: 13
Views: 98

### Re: Bars vs atmospheres

The two are just different units of measurement. Depending on what unit is given and what unit they want in the final answer, you will need to use dimensional analysis to convert between the two. To convert between them, you need to know that 1 bar = 100 kPa (obtained from online) and 1 atm = 101.32...
Wed Jan 08, 2020 5:13 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Module 4 Q17
Replies: 1
Views: 59

### Module 4 Q17

If the initial amounts of CO and H2O were both 0.100 M, what will be the amounts of each reactant and product at equilibrium for the following reaction? Keq = 23.2 at 600K. CO (g) + H2O (g) ⇌ CO2 (g) + H2 (g) Can someone show the step-by-step on how to solve this? I got to the part where I have 0 = ...
Sat Dec 07, 2019 10:58 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 6B.5 Part C
Replies: 1
Views: 82

### 6B.5 Part C

Can someone explain why there are 2 OH-?
Sat Dec 07, 2019 10:27 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 6B.1
Replies: 2
Views: 78

### 6B.1

Why is there a [HCL]0 on the denominator? Isn't the new molarity just going to be 0.12 x [HCL]0 since the molar concentration is reduced to 12% of the initial value?
Sat Dec 07, 2019 11:22 am
Forum: Conjugate Acids & Bases
Topic: Neutralization Equations
Replies: 3
Views: 233

### Neutralization Equations

Looking at question J.7, for neutralization equations in general, since they are balanced, are all of the reactants (and products) going to contain a neutral charge?
And applying this to a broader spectrum, do all chemical equations have reactants and products that have a neutral charge?
Sat Dec 07, 2019 3:41 am
Forum: Bronsted Acids & Bases
Topic: Homework J.7
Replies: 1
Views: 54

### Homework J.7

How do you know the acid and base needed to create zinc nitrite in part C of the question: "Select an acid and a base for a neutralization reaction that results in the formation of (a) potassium bromide; (b) zinc nitrite; (c) calcium cyanide, Ca(CN)2; (d) potassium phosphate. Write the balanced...
Sat Dec 07, 2019 3:17 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Why do acids and bases donate/accept proton?
Replies: 1
Views: 155

### Why do acids and bases donate/accept proton?

Acids and bases, is there a reason why these compounds want to accept/donate a proton? Doing so causes their molecule to be less stable so why do it? Why gain a positive or negative charge when you can remain stable at net charge = 0? This question kind of came up from me trying to understand why KO...
Sat Dec 07, 2019 1:24 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Identifying Acids and Bases
Replies: 2
Views: 145

### Identifying Acids and Bases

Rather than memorizing strong acids and bases (and thus knowing which are weak acids and bases), is there a way to tell from the molecule's structure? Like lone pairs, charges, etc?
Sat Dec 07, 2019 1:21 am
Forum: Lewis Acids & Bases
Topic: List of Strong Acids and Bases
Replies: 2
Views: 92

### List of Strong Acids and Bases

Does anyone know where the list of strong acids and strong bases that we need to know is located?
Fri Dec 06, 2019 3:53 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: Test 2 Question 2 Help
Replies: 2
Views: 91

### Test 2 Question 2 Help

Q2A: "Hydrogen bonding is important for nucleic acids. Draw how two separate nucleic acids below (guanine (G) and cytosine (C)) will interact via H-bonding to form a GC pair." - can someone explain where the H-bonds are and how they're formed? Q2.B: "There are two different base pair...
Fri Dec 06, 2019 3:42 pm
Forum: Electronegativity
Topic: Electronegativity of Atoms We Should Know About
Replies: 4
Views: 176

### Electronegativity of Atoms We Should Know About

Can someone give a hierarchy of the electronegativities of main elements we should know about? Like I know F is the most electronegative and then O (I think?). And then there's C and S that are very similar? I would try to search up periodic tables of them but most give varying values. And I underst...
Fri Dec 06, 2019 3:25 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Oxolate Chelate
Replies: 6
Views: 122

### Re: Oxolate Chelate

Oxalate is bidentate because only two of the oxygens have a minus 1 charge that they use to form a bond with the central metal atom. The other two oxygens form a double bond with the carbon so they have a neutral formal charge. Does it matter if they have a negative bond or not? For molecules like ...