NY Regents Chemistry Exam June 2023: 58-60
Nitrogen dioxide gas, NO2(g), can reach equilibrium with dinitrogen tetroxide gas, N2O4(g), in a closed system. At 1.0 atmosphere, the boiling point of N2O4 is 21°C. The equation below represents this system.
2NO2(g) <---> N2O4(g) + energy
58 Compare the rate of the forward reaction to the rate of the reverse reaction when the system is at equilibrium.
Solution: At equilibrium the rate of the forward reaction is equal to the rate of the reverse reaction.
59 State how the equilibrium shifts when the pressure on the equilibrium system is increased at constant temperature.
Solution: When the pressure increases, equilibrium shifts to the side with less moles of gas. We can use coefficients in front of gaseous molecules to count moles of gas on each side. There are two moles of gas on the left side of the equation and one mole of gas on the right. Therefore, equilibrium will shift to the right side.
60 Compare the entropy of a sample of dinitrogen tetroxide gas at 25°C and 1.0 atmosphere to the entropy of the same sample of dinitrogen tetroxide liquid at 15°C and 1.0 atmosphere.
Solution: Entropy measures disorder. At higher temperature, entropy should be higher. The entropy of dinitrogen tetroxide at 25°C is higher than at 15°C.