## Search found 30 matches

Tue Mar 12, 2019 2:21 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Energies
Replies: 2
Views: 69

### Re: Energies

Hi! The free activation energy refers to Gibbs free energy, which is often used to define the energy barriers of reactions, while the activation energy specifically refers to the amount of energy needed to get over an energy barrier. The activation energy is the difference between the transition sta...
Tue Mar 12, 2019 2:17 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Ordering oxidation and reducing power with E cell
Replies: 1
Views: 84

### Re: Ordering oxidation and reducing power with E cell

Hi! Yes, if you want to order increasing reducing powers, you want to look at what gets oxidized, so it would go from most negative to least negative. Then for increasing oxidizing powers, it would be the reverse, from least negative to most negative.
Tue Mar 12, 2019 2:15 pm
Forum: First Order Reactions
Topic: Rate law with 2 reactants
Replies: 3
Views: 155

### Re: Rate law with 2 reactants

Hi! I think if there are two reactants and the reaction is first order, that means the reaction is not the mechanism and you have to do an experiment to see which reactant affect the overall rate.
Mon Mar 04, 2019 9:51 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Rate determining step
Replies: 2
Views: 135

### Rate determining step

I know that the slowest step in a reaction mechanism is the rate determining step and, if it's the first step, it can be used to calculate the rate law. But, if the first step is not the slow step, how do we find the rate law?
Mon Mar 04, 2019 9:48 pm
Forum: General Rate Laws
Topic: rate and dependence on [R]
Replies: 2
Views: 82

### Re: rate and dependence on [R]

Hi! Yes, reaction rates then only depend on [R] because I think they are the initial rates to make calculations easier.
Mon Mar 04, 2019 9:47 pm
Forum: First Order Reactions
Topic: order
Replies: 5
Views: 195

### Re: order

Hi! The reaction order is essentially the sum of all the exponents of the concentrations in the rate law.
Tue Feb 26, 2019 2:16 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: E˚ vs E
Replies: 13
Views: 1701

### Re: E˚ vs E

Hi! The E nautical (with the circle) means E at standard conditions. The E, however, is just the cell potential in general under any conditions.
Tue Feb 26, 2019 2:15 pm
Forum: Balancing Redox Reactions
Topic: oxidized vs oxidizing agent
Replies: 3
Views: 63

### Re: oxidized vs oxidizing agent

Hi! Oxidation means something that losses electrons. An oxidizing agent is a substance that cause another substance to be oxidized, so in other words it is typically what is reduced.
Tue Feb 26, 2019 2:14 pm
Forum: Balancing Redox Reactions
Topic: Br2(l)-->Br^-(aq)
Replies: 1
Views: 82

### Re: Br2(l)-->Br^-(aq)

Hi! You can tell that it is reduction because the oxidation number of an element in its pure form, such as Br2 is 0 and then it goes to Br^-. Therefore, the oxidation number goes from 0 to -1, indicating a gain of electrons which is reduction.
Wed Feb 20, 2019 1:27 pm
Forum: Administrative Questions and Class Announcements
Topic: Test 2
Replies: 2
Views: 127

### Test 2

Hi, I know the website says the test with cover all topics on Gibbs Free Energy. Does that mean entropy and enthalpy will be specifically covered or only in terms of Gibbs Free Energy?
Wed Feb 20, 2019 1:22 pm
Forum: Van't Hoff Equation
Topic: Equation Purpose
Replies: 2
Views: 147

### Re: Equation Purpose

Hi! Another way to put it is that the Van Hoff equation allows you to calculate k at different temperatures and shows that k is temperature dependent.
Wed Feb 20, 2019 1:19 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta G
Replies: 3
Views: 133

### Re: Delta G

Hi! Also, a positive delta H in the equation deltaG=deltaH-TdeltaS would make it so the entropy and temperature term would have to be positive and greater that the delta H, making it more likely for delta G to be positive, and thus make the reaction not spontaneous.
Mon Feb 11, 2019 7:38 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy equations
Replies: 8
Views: 516

### Entropy equations

In what circumstances would you use the enthalpy equation with the log of volume and which for temperature? I'm just unclear about how the equations are specific to certain situations.
Mon Feb 11, 2019 7:29 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: bond dissociation energy
Replies: 1
Views: 129

### Re: bond dissociation energy

Hi! Because each dissociation energy is given in kJ/mol, you divide the equation by two so you only have to multiply the energy by 1 mole rather than two. In other words, you should be able to get the right answer without dividing, but it just makes calculations easier.
Mon Feb 11, 2019 7:27 pm
Forum: Calculating Work of Expansion
Topic: Question on the units of work
Replies: 3
Views: 123

### Re: Question on the units of work

Hi! I think both are acceptable as long as you make sure there are units attached to your answer.
Mon Feb 04, 2019 3:07 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Degeneracy
Replies: 8
Views: 288

### Degeneracy

Could someone explain what degeneracy tells us and how it can be used? I am still unclear on the topic.
Mon Feb 04, 2019 3:01 pm
Forum: Administrative Questions and Class Announcements
Topic: Chem 14 BL
Replies: 5
Views: 384

### Re: Chem 14 BL

As far as I know, Chem 14BL does not need to be taken with 14C because 14BL focuses on acid-base titrations and 14C moves on to organic chemistry. So, it is best to take 14BL after 14B and before 14C if you don't want the topics to overlap, but you can also take them together (I had a friend do that...
Mon Feb 04, 2019 2:59 pm
Forum: Phase Changes & Related Calculations
Topic: Reversible changes
Replies: 1
Views: 108

### Re: Reversible changes

Hi! Reversible changes refer to physical changes, such as a phase change, and irreversible changes refer to chemical changes, such as combustion.
Tue Jan 29, 2019 3:08 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: enthalpy
Replies: 4
Views: 213

### Re: enthalpy

Hi! Enthalpy being a state function essentially means that the value of enthalpy does not depend on the path taken to obtain that state. In other words, it can be added and subtracted. An example of a state function, like enthalpy, is temperature. When finding the change in temperature, you look at ...
Tue Jan 29, 2019 3:04 pm
Forum: Phase Changes & Related Calculations
Topic: temperature
Replies: 3
Views: 133

### Re: temperature

Hi! During a phase change, the temperature remains constant because the heat added is going to the phase change reaction itself, not towards the temperature. In other words, all of the heat energy is being used to change the phase of the substance. I hope that helps!
Tue Jan 29, 2019 7:57 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cv and Cp
Replies: 2
Views: 75

### Cv and Cp

In class we went over how Cp is usually greater than Cv, why is that? Also how does whether the heat capacity is Cv or Cp change calculations?
Wed Jan 23, 2019 6:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 7th edition 5.35
Replies: 1
Views: 89

### Re: 7th edition 5.35

Hi! For part a, you want to look at how the partial pressures of A, B, and C change. Since A decreases by 10 kPa, B increases by 5 kPa, and C increases by 10 kPa, the coefficients of the balanced equation would be in a 2:1:2 ratio. So, the equation for part A is 2A <=> B + 2C. Then, for part b, usin...
Wed Jan 23, 2019 3:29 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 7th Edition 4A.7
Replies: 1
Views: 86

### 7th Edition 4A.7

Could someone explain how to do 4A.7, specifically why do you have to add the two heat energies, that of the copper pot and of the water?
Wed Jan 23, 2019 3:25 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: How to know when to use partial pressure or molar concentrations?
Replies: 4
Views: 204

### Re: How to know when to use partial pressure or molar concentrations?

Hi! I think unless is specifies to use Kp or convert to partial pressures, if given the molar concentrations you can use those values with gases, as long as you are also using Kc.
I hope that helps!
-Fiona
Tue Jan 15, 2019 2:04 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 7th edition 6B.3
Replies: 1
Views: 46

### Re: 7th edition 6B.3

Hi! For 6B.3 use the 0.025M concentration given to find the desired pH with the formula pH=-log[H3O], since that is essentially the desired concentration. Then, to find the actual concentration in part b, use the equation M1V1=M2V2 with M1=0.025 M, V1=200 mL, V2=250 mL, and solve for M2. Finally, us...
Tue Jan 15, 2019 2:00 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Part 4 Post-Module Question
Replies: 4
Views: 310

### Re: Part 4 Post-Module Question

Hi! The first equation is endothermic, since delta H is positive, so treat temperature as a reactant. If you increase temperature, or increase the amount of reactant, the reaction will shift right towards the products to restore equilibrium. The same logic can be used for the second equation, but si...
Tue Jan 15, 2019 1:57 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: partial pressure
Replies: 2
Views: 67

### Re: partial pressure

Hi! Yes you do when dealing with Kp because the value of Kp will not change with pressure changes, but it can be used to calculate partial pressures.
Thu Jan 10, 2019 3:30 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Table Units
Replies: 4
Views: 170

### ICE Table Units

When completing an ICE table, should you use molarity or moles? Or when should you use molarity and when should you use moles?
Thu Jan 10, 2019 3:22 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Temperature Affecting K
Replies: 2
Views: 86

### Re: Temperature Affecting K

Hi! Another way that may be helpful to think about this is if a reaction is exothermic, treat heat as a product, and if it is endothermic, treat it as a reactant. Then, depending on the situation, if you increase product, the reverse reaction will ensue and K will be lowered and the opposite would h...
Thu Jan 10, 2019 3:13 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K, Kc and Kp
Replies: 8
Views: 198

### Re: K, Kc and Kp

I think K is a general term for the equilibrium constant, while Kc is used when using concentrations and Kp is used with pressures. So, Kc and Kp are both K constants, but are more specific.