Question

Graph 1: Solubility vs. Pressure

Graph 2: Solubility vs. Temperature


Observe the solubility graphs for gaseous solutes. The graph on the left shows how the solubility of a gaseous solute is affected by changes in pressure. The graph on the right shows how the solubility of a gaseous solute is affected by changes in temperature.
According to the graphs, a gas becomes more soluble (solubility increases) in a liquid when
A.
both temperature and pressure are increased
B.
both temperature and pressure are decreased
C.
the temperature is increased and the pressure is decreased
D.
the temperature is decreased and the pressure is increased

Answer 1

According to the typical behavior of gases in relation to solubility:

1. **For pressure:** The solubility of a gas in a liquid increases as pressure increases. This relationship is often described by Henry's Law.

2. **For temperature:** The solubility of a gas in a liquid typically decreases as temperature increases. This is in contrast to solids, where solubility usually increases with temperature.

Given this understanding, let's analyze the options:

- **A. both temperature and pressure are increased**: This would likely lead to decreased solubility, since increasing temperature generally decreases gas solubility.

- **B. both temperature and pressure are decreased**: Decreasing pressure would decrease solubility, and decreasing temperature might increase solubility slightly, but the overall effect would be uncertain.

- **C. the temperature is increased and the pressure is decreased**: This option would decrease solubility since both an increase in temperature and a decrease in pressure are both conditions that decrease gas solubility.

- **D. the temperature is decreased and the pressure is increased**: Decreasing temperature would increase the solubility of the gas, while increasing pressure would also enhance solubility.

Therefore, the correct answer, according to the graphs, is:

**D. the temperature is decreased and the pressure is increased.**