Chapter 18 Practice Test Flashcards
Which of the following is a nonspontaneous event?
a wheelbarrow being moved from one place to another
Which of the following examples of a spontaneous reaction does not involve a chemical energy difference?
a glider (plane) landing on an airport runway
Which of the following events involves a spontaneous reaction that does not include a change in energy?
releasing a gas into the atmosphere
Suppose that, instead of having two connected bulbs, you have three connected bulbs. Assume that you start with the valve closed, add some gas molecules to one bulb, and then remove the valve. Which of the following shows the correct expression for the probability of finding all the gas molecules in one container after 1 hour?
probability = (1/3)x, where x = the number of molecules
Look at the thermal energy drawing.
Which statement about this thermal energy event is not correct?
Heat moving into the house would violate the first law of thermodynamics.
Which statement about enthalpy is not correct?
In a spontaneous reaction, the enthalpy change is always positive.
The second law of thermodynamics says that the entropy of the universe tends to increase. In other words, the universe prefers maximum disorder. With respect to entropy, which statement is not correct?
The temperature does not affect the absolute entropy value.
Look at the plot for entropy, (S°) vs. T (K).
Which statement about this plot is not correct?
There are two ranges in the plot where the temperature of the substance is simply increasing. The value for S° at any point in those ranges can be calculated using the formula
Look at the plot for entropy versus temperature.
Which of the following describes Range B?
the entropy of fusion
With respect to the third law of thermodynamics, which statement is not correct?
At 0 K for a substance, almost all of the thermal energy has been removed from the system
Look at the diagram for the fusion of water (from liquid to solid).
Which statement about this diagram is not correct?
The value for ΔH changes much more than the value for TΔS as the temperature is lowered or raised.
Look at the decomposition reaction for sodium bicarbonate
2NaHCO3(s) <==> Na2CO3(s) + H2O(g) + CO2(g)
Suppose that ΔH = 64.5 kJ/mol and ΔS = 0.167 kJ/mol*K. Which statement about this reaction is correct? Assume that ΔH and ΔS are constant for all the given temperatures
At about 386 K, the reaction is at equilibrium
Which statement about a reaction in which liquid water freezes is not correct?
ΔS is positive.
Calculate the standard free energy of formation of 2 mol of AgCl(s) at 25°C using the given information.
For Ag(s) at 25°C, S° = 42.55 J / mol • K and ΔH°f = 0.0 kJ / mol
For Cl2(g) at 25°C, S° = 222.96 J / mol • K and ΔH°f = 0.0 kJ / mol
For AgCl(s) at 25°C, S° = 96.2 J / mol • K and ΔH°f = −127.07 kJ / mol
−219.5 kJ / mol
The value for ΔG° for the following reaction at 25°C is −394.4 kJ / mol.
C(s, graphite) + O2(g) <==> CO2(g)
Suppose that you raise the temperature to 108°C. What is ΔG° for the reaction at 108°C? (ΔH° = −393.5 kJ / mol and ΔS° = 2.83 J / mol • K)
−394.6 kJ / mol