When you heat a sample of gas at constant volume, which of the following will occur according to the ideal gas law?

• A. The pressure of the gas decreases.
• B. The volume of the gas decreases.
• C. The pressure of the gas increases.
• D. The number of moles of gas increases.

Answer: (C)

Verified step by step guidance

1. Recall the ideal gas law: \(P \times V = n \times R \times T\), where \(P\) is pressure, \(V\) is volume, \(n\) is number of moles, \(R\) is the gas constant, and \(T\) is temperature in Kelvin.
2. Since the volume \(V\) is held constant and the number of moles \(n\) does not change (no gas is added or removed), the equation simplifies to \(P = \frac{nRT}{V}\).
3. When the temperature \(T\) increases, and \(n\), \(R\), and \(V\) remain constant, the pressure \(P\) must increase proportionally to maintain the equality.
4. Therefore, heating the gas at constant volume causes the pressure to increase, not decrease, and the volume does not change.
5. The number of moles \(n\) remains constant because no gas is added or removed during heating.