First Law of Thermodynamics
Second Law of Thermodynamics
Gibbs Free Energy
Kinetics
Molecular Structure
100
What is the definition of the first law of thermodynamics?
The change of internal energy of a closed system will be equal to the heat added to the system minus the work done by the system.
OR
ΔEuniv = ΔEsys + ΔEuniv = 0
100
What is the definition of the second law of thermodynamics?
As energy is transferred or transformed, more and more of it is wasted.
OR
ΔSuniv = ΔSsys + ΔSsurr > 0
100
What is the definition of Gibbs Free Energy?
ΔG = ΔHsys - TΔSsys
100
What is the definition of the equilibrium constant K?
K = Kf/Kr = reactants/products
100
What is the number of electron regions around the sulfur atom in the following?
3
A double bond is a single electron region. Therefore, a single bond, a double bond, and a lone pair form 3 electron regions.
200
What conditions of temperature and pressure are used when measuring the standard enthalpy change of formation?
1 atm pressure; 25 degrees celsius,
200
Calculate ΔSsys for a reaction in which 400 kJ of heat are produced and the temperature increases to 50℃.
1238.39 J/K
200
Suppose that a rxn has ∆H = -28 kJ and ∆S= -60 J/K. At what temperature will it
change from spontaneous to non-spontaneous?
A. 467 K
B. 500 K
C. 50
D. 46.7 K
A. 467 K
200
In the combustion of methane, CH4(g) + 2 O2(g) → CO2(g) + 2 H2O (g), find the reverse rate law.
Rr = Kr[CO2][H2O]2
200
Which molecule has the larger bond angle?
NO3-
OR
BrO4-
NO3- > BrO4-
NO3- = 120o
BrO4- = 109o
300
What is the enthalpy change of the following reaction:
H-H → 432 kJ/mol
O=O → 494 kJ/mol
H-O → 459 kJ/mol
-478 kJ/mol
300
What is the relative change in entropy when H2O in solid form sublimates?
ΔS > 0
300
The entropy and enthalpy of a reaction are both negative. Is the reaction spontaneous?
The reaction will be spontaneous if and only if the magnitude of the enthalpy is greater than the magnitude of the entropy times the temperature.
300
For the reaction A + 3B → 2C, how does the rate of disappearance of B compare to the rate of production of C?
A. the rate of disappearance of B is 1/2 the rate of appearance of C
B. the rate of disappearance of B is 3/2 the rate of appearance of C
C. the rate of disappearance of B is 2/3 the rate of appearance of C
D. the rate of disappearance of B is 1/3 the rate of appearance of C
B. the rate of disappearance of B is 3/2 the rate of appearance of C
300
What is the hybridization around the right most O in Ozone (O3)?
O3 has four electron regions, so it is sp3 hybridized. The four hybrids are used in two σ bonds (O–H and C–O) and two lone pairs that are not shown. Oxygen obeys the octet rule, so lone pairs must frequently be added to give oxygen an octet.
400
What is the enthalpy change of the following reaction:
2C2H6 + 7O2 --> 4CO2 + 6H2O
-2842 kJ/mol
400
A liquid at 25℃ freezes at -10 ℃ with a change in entropy of -2,103.23 J/K. How much energy was absorbed by the system in kJ?
-553.15 kJ
Use Delta s = q/t = heat(j)/temp(k)
400
Of the following reactions, which of the following is only spontaneous at high enough temperatures?
A. ∆H –, ∆S +
B. ∆H –, ∆S –
C. ∆H +, ∆S –
D. None of the Above
E. ∆H +, ∆S +
∆H +, ∆S +
400
If the equilibrium is established by initially adding 0.10 mol each of A and B to a 1L container, then which of the following must be true once the mixture achieves equilibrium?
A + 2B ⇋ 2C K = 320
a. [A] = [B]
b. [A] = [B] = [C]
c. [B] = 2[C]
d. [A] > [B]
e. [A] < [B]
d. [A] > [B]
400
Lewis structure and bonding in tetrafluoroethylene (C2F4):
ER = 6(8) = 48 electrons required with no sharing
VE = 2(4) from C + 4(7) from F = 36 valence electrons
SP = 1/2(48 - 36) = 6 shared pairs
How many π bonds are there?
There is one π bond in the C=C double bond.
500
What is the change in ΔE of reaction coordinate (A) below:
~ 15 kJ
500
Which state change would cause the most negative change in entropy?
Gas to solid.
500
If a reaction has a positive value for its enthalpy and a negative value for its entropy, which of the following is true?
The reaction is nonspontaneous
Not enough information to tell
The reaction is at equilibrium
The reaction is spontaneous
The reaction is nonspontaneous
500
Concept Question: Given a K value of 0.43 for the following aqueous equilibrium, suppose sample Z is placed into water such that it’s original concentration is 0.033 M. Assume there was zero initial concentration of either A(aq) or B(aq). Once equilibrium has occurred, what will be the equilibrium concentration of Z?
2A(aq) + B(aq) ⇋ 2Z(aq) K = 0.43
a. more than 0.033 M c. 0.033 M exactly
b. less than 0.033 M d. there is no way to tell
b. less than 0.033 M
500
Below is the MO diagram for He2. What type of MO does the He2 form?
Nonbonding MO
Each He atom has two electrons in its 1s orbital, so the two-atom system has four electrons. Two electrons would be placed in the σ orbital and two in the σ*. However, ΔE* > ΔE, so the energy of four electrons in He2 is more significant than in two separated He atoms. The bond order of the He-He bond would be 1/2(2 − 2) = 0, no bond. Consequently, He2 does not form.