## Search found 39 matches

Sun Mar 17, 2019 12:24 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Change in Equilibrium Constant
Replies: 1
Views: 206

### Change in Equilibrium Constant

Is there anything other than temperature that will change the value of an equilibrium constant K?
Mon Mar 11, 2019 11:21 pm
Forum: General Rate Laws
Topic: what if
Replies: 3
Views: 95

### Re: what if

You can't just make it first order. The order of a reaction is determined empirically and cannot be changed. However, if you had a reaction that was simply first order the rate law would appear as Rate = k[A]. Also, a second order rate law is rate = k[A]2.
Mon Mar 11, 2019 11:18 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Molecularity
Replies: 2
Views: 58

### Re: Molecularity

It is not in the outline so most likely not, however you should always have an understanding of any material covered in class.
Mon Mar 11, 2019 11:16 pm
Forum: Ideal Gases
Topic: ICE
Replies: 8
Views: 141

### Re: ICE

A value with less than 10^-3 means that we can approximate the x value.
Mon Mar 04, 2019 9:46 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Enot
Replies: 2
Views: 95

### Re: Enot

Eo is a state function. E is not a state function.

This is because Eo is related directly to ΔGo (-nFEo = ΔGo)
Mon Mar 04, 2019 9:42 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Galvanic Cells
Replies: 4
Views: 110

### Re: Galvanic Cells

Eventually the reaction that occurs between the two sides will complete/ be at equilibrium.
Mon Mar 04, 2019 9:41 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6th edition 14.47
Replies: 4
Views: 123

### Re: 6th edition 14.47

I got the same answer, it seems as though they chose to round early from 14.7 to 15. However, this would not explain the discrepancy.
Tue Feb 26, 2019 10:43 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Writing Balanced Equations for Galvanic Cells (14.11 part d sixth edition)
Replies: 3
Views: 94

### Re: Writing Balanced Equations for Galvanic Cells (14.11 part d sixth edition)

For the cathode, try to imagine the Oxygen as being the electrons supplied to make the OH-. When it is added to water it will increase the number of electrons and form OH-. (Really it is the electrons adding on with the oxygen)
Tue Feb 26, 2019 9:52 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Replies: 1
Views: 52

### Re: Question about reducing/oxidizing ability

Check the E values. A lower (more negative) E value has a higher reducing ability.
Mon Feb 25, 2019 9:55 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Replies: 1
Views: 47

I don't understand how to split up the half reactions for this equation. In the solution manual, it reduces a random Ag + ion and I don't know where it comes from. Does anyone understand where the silver ion came from? It also seems as though silver has just been added in as an electrode in the prob...
Mon Feb 25, 2019 9:45 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: When to use Platinum
Replies: 5
Views: 119

### When to use Platinum

In a galvanic cell, when do you use an electrode? (As in an added on one, it seems to most commonly be platinum).

How do you decide which element to use as the extra electrode?
Wed Feb 20, 2019 3:58 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs and concepts
Replies: 3
Views: 81

### Re: Gibbs and concepts

You will also probably need to know if a reaction is exergonic or endergonic based on the value of G.
Wed Feb 20, 2019 3:57 pm
Forum: Van't Hoff Equation
Topic: when to use
Replies: 4
Views: 111

### Re: when to use

When you want to find the relation between a change in temperature and a change in Keq.
Wed Feb 20, 2019 3:55 pm
Forum: Administrative Questions and Class Announcements
Topic: Test 2
Replies: 2
Views: 100

### Re: Test 2

You will most likely have to calculate entropy and enthalpy in order to use it with Gibbs free energy.
Wed Feb 20, 2019 3:54 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Question 9.23 (Sixth Edition)
Replies: 1
Views: 249

### Re: Question 9.23 (Sixth Edition)

They are both trigonal planar, so try to find which one is the least symmetrical, as in when you rotate the molecule, which has the more states. This will have the most entropy.

(COF2 in this case)
Wed Feb 20, 2019 3:51 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Question 9.19 (Sixth Edition)
Replies: 1
Views: 71

### Re: Question 9.19 (Sixth Edition)

This question needs to be done in parts, remember that entropy is a state function, so as long as you end up with 85 being your final temperature, you can do whatever you want along the way. Try splitting up the entropy into 3 parts: what it takes to go from 85-100, at 100, then back down again.
Wed Feb 20, 2019 3:50 pm
Forum: Administrative Questions and Class Announcements
Topic: midterm
Replies: 2
Views: 98

### Re: midterm

If you were unable to get them after the lecture, you can go to your TA's office hours as well.
Mon Feb 11, 2019 11:19 pm
Forum: Phase Changes & Related Calculations
Topic: Delta H
Replies: 11
Views: 241

### Re: Delta H

A Positive ΔH is an endergonic reaction. A negative ΔH is an exergonic reaction.
Mon Feb 11, 2019 9:50 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: q and w = 0
Replies: 3
Views: 109

### Re: q and w = 0

If an ideal gas is "isothermal" then you can assume ΔU = 0.
Mon Feb 11, 2019 3:48 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: When to use differential form
Replies: 2
Views: 94

### When to use differential form

When do I use ΔS=q/t instead of ΔS= nC(ln(T2/T1))
Mon Feb 04, 2019 6:06 pm
Forum: Ideal Gases
Topic: Ideal gas constant R
Replies: 10
Views: 412

### Re: Ideal gas constant R

Look at the units you are dealing with, the constants have different units. So if you don't know try looking at what units you are using and comparing them to the units of the gas constants.
Mon Feb 04, 2019 6:02 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Kb meaning
Replies: 2
Views: 67

### Re: Kb meaning

When you don't have Avogadro's number you get a different result than the gas constant.
Mon Feb 04, 2019 6:01 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Cup of Tea
Replies: 17
Views: 538

### Re: Cup of Tea

An open cup of tea can have its matter and energy changed. It fully interacts with the surroundings.
Sun Jan 27, 2019 4:06 pm
Forum: Phase Changes & Related Calculations
Topic: Delta H
Replies: 11
Views: 241

### Re: Delta H

Delta refers to the change between the final and the initial of value. When you have a negative delta H this is due to the fact that you have lost enthalpy, so it makes sense that the reaction would be exothermic (give off heat). The reverse is true for a reaction with positive delta H. It is an end...
Sun Jan 27, 2019 4:04 pm
Forum: Ideal Gases
Topic: SI Units
Replies: 5
Views: 288

### Re: SI Units

Atmospheres. (atm).
Sun Jan 27, 2019 4:03 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Heat vs Enthalpy
Replies: 4
Views: 83

### Re: Heat vs Enthalpy

Enthalpy is a state property, which means that it measures the total of an object at a specific moment. It is a value that is not influenced by how it was achieved, all that matters is what it is.
Mon Jan 21, 2019 1:48 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: difficulties recognizing weak acids and bases
Replies: 9
Views: 642

### Re: difficulties recognizing weak acids and bases

It can help to draw a Lewis structure and look for any lone pairs, or any hydrogens that could be donated.
Mon Jan 21, 2019 1:39 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Polyprotic Equations
Replies: 1
Views: 33

### Re: Polyprotic Equations

You would add the hydronium created in the first equation to the initial value of hydronium of the next equation.
Mon Jan 21, 2019 1:38 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Strong acids and bases
Replies: 4
Views: 82

### Re: Strong acids and bases

You can also get a clue based on the Ka or Kb given. A large number means it will dissociate strongly.
Tue Jan 15, 2019 10:00 am
Forum: Ideal Gases
Topic: #47 on Chemical Equilibrium 1B Video Module Assessment
Replies: 3
Views: 93

### Re: #47 on Chemical Equilibrium 1B Video Module Assessment

Use PV=nRT, then convert it to P=MRT, (n/v = concentration = M) Then proceed to use the values given in concentrations to solve for the pressures individually. These are the partial pressures.
Tue Jan 15, 2019 9:57 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Help on 12.39
Replies: 1
Views: 41

### Re: Help on 12.39

They are, it's just that they have a hydroxide with them in table 12.2. Use the Kb given in the table to convert into Ka.
Tue Jan 15, 2019 9:54 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Question on 12.41
Replies: 3
Views: 74

### Re: Question on 12.41

The others are acids, not bases so they can be found in table 12.1, except bonded to another element (generally hydrogen) this gives you the Ka value instead of the Kb value. This means that you can can subtract the pKa from 14 to find the pKb.
Tue Jan 15, 2019 9:46 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Reaction Quotient
Replies: 10
Views: 218

### Re: Reaction Quotient

The reaction quotient is calculated during the reaction, rather than at the end. Depending on its value it can give you information about how the reaction will proceed (e.g. if Q>K then there are too many products and it will favour the left).
Wed Jan 09, 2019 4:36 pm
Forum: Ideal Gases
Topic: Inert Gases
Replies: 3
Views: 71

### Re: Inert Gases

Most likely it's because inert gases won't react (because they have full valence shells), therefore they won't change the chemical equation in any way.
Wed Jan 09, 2019 4:34 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: finding K Value
Replies: 3
Views: 49

### Re: finding K Value

This is because you raise the concentration or partial pressure to the power of its respective coefficient in the equation. When you divide an exponent by 2 it is the same thing as square rooting. Or when you multiply it by 2 it is the same as squaring it. As an example: 2 (3/2) = sqrt(2 3 )...
Wed Jan 09, 2019 4:28 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Calculating the Equilibrium Composition in ATP Hydrolysis
Replies: 4
Views: 50

### Re: Calculating the Equilibrium Composition in ATP Hydrolysis

That number will be equal to the concentration of ADP and Pi. This is due to the fact that the coefficients for ATP and ADP and Pi are all the same (1) so when you lose a certain concentration of ATP, you lose the same concentration of ADP and Pi.
Wed Jan 09, 2019 4:26 pm
Forum: Ideal Gases
Topic: use
Replies: 8
Views: 101

### Re: use

If you mean P = (n/V)*R*T, you would use that in order to solve for concentration (n/V is the concentration) when given a pressure.

If you mean k = (P.products)/(P.reactants) you would use that to solve for the equilibrium constant or partial pressures, depending on your initial information.
Wed Jan 09, 2019 4:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: [Cl2] vs (PCl2)
Replies: 1
Views: 26

### Re: [Cl2] vs (PCl2)

The square brackets refer to the concentration of Cl2 which is its molarity.
The "P" refers to the partial pressure of Cl2, which is generally given in atm.
Wed Jan 09, 2019 4:18 pm
Forum: Ideal Gases
Topic: use
Replies: 8
Views: 101

Which Equation?