CHEMISTRY COMMUNITY

Rishi Khettry 1L

(3/2)*R deals with an ideal gas at a constant volume

Rishi Khettry 1L

Exothermic processes give off heat while endothermic processes absorb heat. It is important to identify which you consider to be the system and which are the surroundings.

Rishi Khettry 1L

By looking at standard reduction potentials, you can determine the reducing or oxidizing power. The more positive the potential, the greater the electron pulling power of the reduction half-reaction which means it is more likely to be reduced.

Rishi Khettry 1L

Usually the problem will specify a unit of time and we would want to use that same unit of time for K. Otherwise, using units of time as seconds is usually a safe bet.

Rishi Khettry 1L

Intermediates will always be consumed while catalysts are not consumed.

Rishi Khettry 1L

We will likely be given the half reactions and the potentials along with them similar to our test.

Rishi Khettry 1L

Gibbs free energy does not apply only to nonexpansion work

Rishi Khettry 1L

Heat is leaving the body so you regard the body as the "system" and therefore q is negative

Rishi Khettry 1L

Extensive is dependent while intensive is independent

Rishi Khettry 1L

Calculate cathode - anode substituting both numbers and the combination that gives the most positive output is the correct one

Rishi Khettry 1L

n is the number of electrons

Rishi Khettry 1L

The sign indicates standard state which means it is taking place under standard conditions (aka 25 degrees Celsius and 1 atm)

Rishi Khettry 1L

Residual enthalpy can be calculated when a reaction is taking place at a very low temperature almost close to 0

Rishi Khettry 1L

The term free expansion implies work is = 0 and in that case q would also be zero as the deltaU value needs to remain 0

Rishi Khettry 1L

A was the more precise answer but if you put B, you were given points back.

Rishi Khettry 1L

It is important to know the difference between state functions and those that aren't state functions. Entropy and enthalpy are state functions while heat and work are not.

Rishi Khettry 1L

since the problem says "same temperature" we can infer it is isothermal which means deltaU is zero. Expansion work is occurring as the balloon grows

Rishi Khettry 1L

Separating the steps allows us to perform two different calculations which would give us the final correct answer. It is impossible to calculate them simultaneously as there is not an equation we have learned to allow us to deal with both forms of energy change at the same time.

Rishi Khettry 1L

The only way to change the internal energy of a closed system is to transfer energy into it as heat or work

Rishi Khettry 1L

Hsub can also be deltaH(fusion) + deltaH(vaporization)

Rishi Khettry 1L

if you convert all given mmol values to mol values and then run the calculation, you should get the correct answer as given in the solutions manual

Rishi Khettry 1L

We may be given K values or will be told which is step is the fast or slow one. Always remember the slow step is the rate-determining step.

Rishi Khettry 1L

We know the reaction is isothermal because it takes place in a thermally insulated vessel. At a constant temperature, these reactions are usually reversible

Rishi Khettry 1L

The unique reaction rate depends on the coefficients of the reaction

Rishi Khettry 1L

Be sure to remember with n_r that the unit "mol" isn't incorporated

Rishi Khettry 1L

Hi Megan!
Although sometimes understanding the units can be quite difficult, in class, Dr. Lavelle mentioned either unit would be correct.
Just be sure to make the units for your Gibbs Free Energy of formation to be in "per mole".
Good luck!

Rishi Khettry 1L

Yes with a positive deltaG, the reaction is not spontaneous in the forward direction but will be spontaneous if reversed.
With a negative deltaG, the reaction IS spontaneous in the forward direction but not so if reversed.

Rishi Khettry 1L

Calculations about internal energy and work were omitted from the first test because Dr. Lavelle felt we had not covered it as well as we needed to at the time.
He expects us to be able to do calculations for both internal energy and work on the midterm!

Rishi Khettry 1L

To clarify, intensive properties are ratios. For example, density would be an intensive property because it is mass/volume. Where mass and volume are both extensive properties.

CHEMISTRY COMMUNITY

Search found 29 matches

Re: 8.103

Re: Endothermic/exothermic

Re: Ranking elements

Re: k

Re: Identifying a catalyst in a reaction

Re: Half-Reactions Sheet

Re: Gibb's Energy and Work

Re: 9.1

Re: Why is entropy extensive?

Re: determining cathode from anode

Re: Finding n

Re: Standard Gibbs

Re: S=klnW

Re: Isothermal system

Re: Midterm #6A

Re: State functions?

Re: Test 1 #3

Re: change in internal energy

Re: The First Law

Re: enthalpy of sublimation

Re: Help on 15.3

Re: Slow and Fast Steps

Re: Reversible or irreversible?

Re: Unique Reaction Rates [ENDORSED]

Re: Nernst Equation

Re: Units of S and H

Re: Gibbs Free Energy and Spontaneity

Re: Calculations on Internal Energy

Re: Useful Summary of Thermodynamic Definitions