## Search found 50 matches

Sat Mar 14, 2020 8:56 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Mnemonic for Oxidation and Reduction
Replies: 7
Views: 137

### Re: Mnemonic for Oxidation and Reduction

It's used in the book so I'm not sure if you already know this one but Red Cat, An Ox is super helpful for me (REDuction = CAThode, ANode = OXidation)
Mon Mar 09, 2020 11:29 pm
Forum: General Rate Laws
Topic: Homework 7A.1
Replies: 4
Views: 77

### Re: Homework 7A.1

for b, since only 2 moles of nh3 are formed for every 3 moles of h2, nh3 is formed 2/3 times as fast as h2 is used. the same is true for n2 and nh3.
Mon Mar 09, 2020 11:24 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Replies: 7
Views: 44

Okay that makes sense. One more question, what does adhesion/adsorption have to do with catalysts?
Mon Mar 09, 2020 11:22 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: How to determine slow step?
Replies: 9
Views: 85

### Re: How to determine slow step?

I don't think there is a way to determine it unless the problem tells you
Mon Mar 09, 2020 11:21 pm
Forum: First Order Reactions
Topic: Determining Order
Replies: 7
Views: 63

### Determining Order

If we are not given a graph, how do you determine the order of a reaction? Do we have to write out all the reaction mechanism steps?
Mon Mar 09, 2020 11:19 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts and Equilibrium
Replies: 2
Views: 21

### Re: Catalysts and Equilibrium

Catalysts just lower the activation energy but don't affect the overall products and reactants.
Mon Mar 09, 2020 11:18 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Replies: 7
Views: 44

Can someone please explain what adsorption is in simple words? I wrote down Dr. Lavelle's explanation and I've read other people's answers on other posts but it still doesn't make sense to me
Mon Mar 09, 2020 11:09 pm
Forum: First Order Reactions
Topic: Half Life
Replies: 13
Views: 156

### Re: Half Life

If only the rate constant is given or can be found, or the question mentions something about half of the substance remaining, then you would probably need to find the half life
Mon Mar 09, 2020 11:00 pm
Forum: General Rate Laws
Topic: integrated rate law vs general
Replies: 8
Views: 121

### Re: integrated rate law vs general

When they ask for the rate at a certain time you should use the integrated rate law
Fri Mar 06, 2020 12:29 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Inert electrode
Replies: 9
Views: 81

### Re: Inert electrode

You add it when there's no conducting solid in the given reaction
Fri Mar 06, 2020 12:25 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Purpose of Electrode
Replies: 9
Views: 157

### Re: Purpose of Electrode

Sorry one more question! How would you write the electrode in a cell diagram?
Fri Mar 06, 2020 8:45 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Signs of Enaught
Replies: 7
Views: 80

### Signs of Enaught

What does it mean when Enaught is negative and why is it always positive for a galvanic cell?
Fri Mar 06, 2020 8:40 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Purpose of Electrode
Replies: 9
Views: 157

### Purpose of Electrode

What does the electrode do in a cell? Why do we sometimes add platinum as an electrode?
Fri Mar 06, 2020 8:39 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Reducing Mass of Electrode
Replies: 6
Views: 121

### Reducing Mass of Electrode

Does halving the mass of the electrode affect the cell potential? If so, how?
Fri Mar 06, 2020 8:37 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Calculating ln Q
Replies: 20
Views: 222

### Re: Calculating ln Q

Yes because the right side is the cathode (gaining electrons) while the left is the anode (losing electrons).
Fri Mar 06, 2020 8:32 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: K in 6.65
Replies: 2
Views: 62

### Re: K in 6.65

Could you post the question?
Fri Mar 06, 2020 8:21 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Nernst Equation for Concentration Cells
Replies: 6
Views: 81

### Re: Nernst Equation for Concentration Cells

E°cell is 0, Then like the person above me said, you just need to find n and Q since T is given and F and R are constants.
Fri Mar 06, 2020 8:17 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Units G=-nFE
Replies: 6
Views: 154

### Units G=-nFE

I'm not sure if this is common sense, but if the units for F are coulombs and the units for E are volts, how do we get joules for G?
Sun Feb 09, 2020 12:56 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.7
Replies: 4
Views: 37

### Re: 4D.7

I think if it's ever the difference in T (delta T), then there's no need to convert. However, if you're using T to calculate something else, like in the ideal gas equation, then you need to convert to Kelvin!
Sat Feb 08, 2020 11:46 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.7
Replies: 4
Views: 37

### Re: 4D.7

Thank you! Is this always going to be the case if there is no given temperature?
Sat Feb 08, 2020 11:02 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D.7
Replies: 4
Views: 37

### 4D.7

The question reads: Oxygen difluoride is a colorless, very poisonous gas that reacts rapidly and exothermically with water vapor to produce O2 and HF: OF2(g) + H2O(g) -> O2(g) + 2 HF(g) deltaH = -318 kJ What is the change in internal energy for the reaction of 1.00 mol OF2? I understand that we have...
Thu Feb 06, 2020 10:20 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Question from Wednesday Lecture
Replies: 3
Views: 72

### Re: Question from Wednesday Lecture

The process is defined as an isothermal reversible expansion! So, no heat is transferred.
Thu Feb 06, 2020 10:18 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Value for T
Replies: 1
Views: 24

### Value for T

When calculating deltaS = q/T, does T always have to be in Kelvin or is degrees Celsius okay?
Thu Feb 06, 2020 10:17 pm
Forum: Calculating Work of Expansion
Topic: Reversible vs. Irreversible
Replies: 3
Views: 61

### Re: Reversible vs. Irreversible

Reversible reactions are always at equilibrium (entropy = 0) because all energy lost from expansion is replaced by the surrounding heat! In contrast, irreversible reactions occur quickly - too quickly for the energy to be replaced.
Thu Feb 06, 2020 10:11 pm
Forum: Phase Changes & Related Calculations
Topic: Heating Curve Phase Changes
Replies: 11
Views: 88

### Heating Curve Phase Changes

Why is the heating curve flat when changing phases of a substance?
Thu Feb 06, 2020 10:05 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Water and Equilibrium
Replies: 2
Views: 28

### Re: Water and Equilibrium

Water as a liquid is usually disregarded in the equilibrium constant simply because it is a solvent, as Elena said before me. H2o(g) is not present in as large of a relative concentration as H2O(l) is when it is used as the solvent, so changing H2o(g) would affect the constant!
Thu Feb 06, 2020 10:00 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: pKa and pKb
Replies: 3
Views: 53

### Re: pKa and pKb

Also, Ka is calculated using the equation [H3o+][A-]/[H], while Kb is calculated using [OH-][BH+]/{B]
Fri Jan 31, 2020 12:46 am
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Standard Form of molecule
Replies: 6
Views: 88

### Re: Standard Form of molecule

As long as the pressure is 1 atm and the temperature is 25C, the substance is in its standard form.
Fri Jan 31, 2020 12:44 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta G° vs Delta G
Replies: 2
Views: 28

### Delta G° vs Delta G

What's the difference between Delta G° and Delta G?
Fri Jan 31, 2020 12:43 am
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Reversible Reactions
Replies: 5
Views: 50

### Reversible Reactions

What does it mean for a reaction to be reversible? Why are small changes associated with them?
Fri Jan 31, 2020 12:40 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: state property
Replies: 8
Views: 57

### state property

What exactly is a state property? I understand that it only depends on the initial and final positions, but I don't understand what that means fundamentally. Also, what is something that is not a state property?
Fri Jan 31, 2020 12:37 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: 4B.9
Replies: 3
Views: 35

### Re: 4B.9

Since q = 0, the only way for deltaU to also be 0 is if w is 0 :)
Fri Jan 31, 2020 12:29 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Test #1// #5
Replies: 5
Views: 73

### Re: Test #1// #5

Fri Jan 24, 2020 12:14 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Assuming X
Replies: 3
Views: 36

### Re: Assuming X

Yes, I believe so
Fri Jan 24, 2020 12:13 am
Forum: Calculating Work of Expansion
Topic: Reversible vs. Irreversible Reactions
Replies: 2
Views: 25

### Reversible vs. Irreversible Reactions

What does it mean for a reaction to be reversible?
Fri Jan 24, 2020 12:12 am
Forum: Calculating Work of Expansion
Topic: Same Initial and Final States
Replies: 1
Views: 32

### Same Initial and Final States

Why does gas do more work for reversible, isothermal expansion than for constant external pressure given the initial and final states are the same? Page 243 of the textbook states that "a change carried out reversibly always does more work than a change carried out irreversibly," but I don...
Thu Jan 23, 2020 11:31 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5.35
Replies: 1
Views: 38

### Re: 5.35

You look at the ratio of change! If we were to draw an ICE table, the reactant 2A would have its partial pressure changed by -2x, as opposed to A which would have a -x change. B has a change of 5, C has a change of 10, and A has a change of -10, so the reaction is 2A -> B + 2C
Thu Jan 23, 2020 7:58 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5.61f
Replies: 5
Views: 45

### Re: 5.61f

I think since the reaction is a dilute solution, changing the concentration of water doesn't affect the reaction since there's already so much of it!
Thu Jan 16, 2020 5:28 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Negative pH
Replies: 6
Views: 45

### Negative pH

Can a pH be 0 or negative? If so, what would that mean?
Thu Jan 16, 2020 5:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Acid Strength and Oxidation Number
Replies: 2
Views: 57

### Re: Acid Strength and Oxidation Number

That makes sense, thank you!
Thu Jan 16, 2020 5:19 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Cubic functions
Replies: 3
Views: 22

### Cubic functions

If we are given a Ka such as [X]^2[H3O+] / [HX2] and solving for x leads to a cubic function, how are we supposed to find that using a calculator?
Thu Jan 16, 2020 5:12 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Acid Strength and Oxidation Number
Replies: 2
Views: 57

### Acid Strength and Oxidation Number

Why does acid strength increase as oxidation number increases? I read the section in the textbook but I still don't understand.
Thu Jan 16, 2020 5:01 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Endo/Exothermic Reactions
Replies: 6
Views: 77

### Endo/Exothermic Reactions

Are all reactions like X2 -> 2X going to be endothermic?
Thu Jan 16, 2020 4:59 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Inert gas
Replies: 4
Views: 27

### Inert gas

Is an inert gas a noble gas or is it just any gas not in the reaction?
Thu Jan 09, 2020 8:03 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Catalyst and Equilibrium
Replies: 2
Views: 18

### Catalyst and Equilibrium

Does adding a catalyst to the reaction affect the concentration of reactants and products at equilibrium? Thank you in advance.
Thu Jan 09, 2020 7:59 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Volume and Equilibrium
Replies: 3
Views: 32

### Volume and Equilibrium

Does changing the volume of a reaction affect equilibrium? How does it change? Thank you.
Thu Jan 09, 2020 7:51 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Calculating K 5I.33
Replies: 2
Views: 26

### Calculating K 5I.33

In the case that only mass is given, would we have to convert to moles first to find the K value? Thank you!
Thu Jan 09, 2020 7:32 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: multiplied reaction
Replies: 3
Views: 42

### Re: multiplied reaction

If you find K for the original problem, you get something along the lines of K= [NH3}^2 / [N2][H2]^3 The K value for the other problem is K = [NH3}^4 / [N2]^2[H2]^6 which can be simplified to {[NH3}^2 / [N2][H2]^3}^2 Therefore, the K value of the other problem is K^2 of the original problem. I hope ...
Thu Jan 09, 2020 7:24 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Composite Equations
Replies: 2
Views: 32

### Composite Equations

From the solutions manual, I know that when you add two equations, you have to multiply the K values, but can someone explain why the K values are multiplied instead of just added?
Thu Jan 09, 2020 7:06 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5G.7
Replies: 5
Views: 49

### Re: 5G.7

Either concentration or partial pressure can be used for gases. Gases have a concentration too as defined by the n/V in the Ideal Gas Law. In this case, partial pressure is just given so we use it!