If a gas is compressed isothermally, which of the following statements is true?

• A. The temperature of the gas increases as the volume decreases.
• B. The pressure of the gas increases as the volume decreases.
• C. The pressure of the gas decreases as the volume decreases.
• D. The volume of the gas remains constant as the pressure increases.

Answer: (B)

Verified step by step guidance

1. Understand the meaning of an isothermal process: it is a process in which the temperature of the gas remains constant throughout the compression or expansion.
2. Recall the ideal gas law: \(P \times V = n \times R \times T\), where \(P\) is pressure, \(V\) is volume, \(n\) is the number of moles, \(R\) is the gas constant, and \(T\) is temperature.
3. Since the temperature \(T\) is constant in an isothermal process, the product \(P \times V\) must remain constant (Boyle's Law).
4. Analyze what happens when the volume \(V\) decreases: to keep the product \(P \times V\) constant, the pressure \(P\) must increase.
5. Conclude that during isothermal compression, the pressure of the gas increases as the volume decreases, while the temperature remains constant.