SI Chem 178
Ch 14, 19
Leader: Emily
Date: 4/8/2013
Review: Ch 14
14.21 CH3NC  CH3CN (Isomerization reaction)
Time (s)
[CH3NC] (M)
0
0.0165
2,000
0.0110
5,000
0.00591
8,000
0.00314
12,000
0.00137
15,000
0.00074
a. Calculate the average rate of reaction from 5,000s to 12,000s. Then calculate the
average rate of reaction over the course of the experiment.
14.27 Rxn: A + B  C Rate Law: Rate= K[B]^2
a. If [A] is doubled, how will the rate be affected? Will k change?
b. What are the reaction orders for [A] and [B]
c. What are the units of k in this case?
14.36 Rxn: 2NO(g) + O2(g)  2NO2(g)
Experiment #
[NO] (M)
[O2] (M)
Initial Rate (M/s)
1
0.0126
0.0125
1.41x10^-2
2
0.0252
0.0125
5.64x10^-2
3
0.0252
0.0250
1.13x10^-1
a. What’s the rate law? (generalized)
b. What are the units of k?
c. What is the average value of the rate constant calculated from each of the 3
experiments?
d. What is the rate when [NO]=0.075M and [O2]=0.0100M?
e. If the previous data were in terms of disappearance of NO, what is the rate of
disappearance of [O2] at the same concentrations?
14.76 See Doc Cam
14.64 NO decomposes to N2 and O2, it’s second order and has a rate constant of 0.0796
M-1 s-1at 737 Deg C, at 947 Deg C, its rate constant is 0.0815 M-1 s-1. What is its Ea?
Review linearity of graphs, molecularity of elementary rxns.
Ch 19
19.15 Consider – Vaporization of water to steam at 1 atm
a. Is this process endo- or exothermic?
b. In what temperature range is this spontaneous?
c. When is this phase change non-spontaneous?
d. What temperature keeps the phases in equilibrium?
19.26 Gallium (Ga) freezes at 29.8*C, its Hfusion= 5.59kJ/mol
a. When Ga solidifies, is its S + or - ? Why?
b. Calculate the value of S when 60g of Ga solidifies at 29.8*C. (Mw=69.72g/mol)
19.27/28 a. Express the second law of thermodynamics in words and as a mathematical
expression – consider reversibility.
b. In a particular spontaneous process, S decreases by X. What can you conclude must
be true about Ssurr (sign and magnitude)?
c. In a reversible process, Ssurr = -78 J/K, what can you conclude about Ssys?
19.33 How would each of the following affect the # of microstates in a system?
a. Increase in temp
b. Decrease in volume
c. Changing state from liquid to gas
Increasing a system’s microstates increases __________________.
19.44 Predict the sign of Ssys for the following:
a. Molten gold solidifies
b. Cl2 dissociates into 2 Cl molecules in the stratosphere
c. Gaseous CO and H2 interact to form liquid methanol.
d. Calcium phosphate precipitates from mixing Ca(NO3)2(aq) and (NH4)3PO4(aq).
19.53 Calculate the S for the following (I’ll put appendix C up on the doc cam)
a. C2H4(g) + H2(g)  C2H6(g)
b. N2O4(g)  2NO2(g)
c. Be(OH)2(s)  BeO(s) + H2O(g)
d. 2CH3OH(g) + 3O2(g)  2CO2(g) + 4H2O(g)
19.39 b. Distinguish between rotational, translational, and vibrational energies.
19.40 a. If we are told the entropy of a system is 0, what can we conclude about the
system and its temperature? Which law tells us this?