An 80 g sample of oxygen gas (O_2) was heated from 25°C to 225°C at constant pressure. Using the ideal gas law, what happens to the volume of the gas?

• A. The volume increases because temperature increases.
• B. The volume decreases because pressure is constant.
• C. The volume decreases because temperature increases.
• D. The volume remains the same because mass is constant.

Answer: (A)

Verified step by step guidance

1. Identify the variables involved in the problem: the mass of oxygen gas (80 g), the initial temperature (25°C), the final temperature (225°C), and the fact that pressure is constant.
2. Convert the temperatures from Celsius to Kelvin because the ideal gas law requires absolute temperature. Use the formula \(T(K) = T(°C) + 273.15\) for both initial and final temperatures.
3. Recall the ideal gas law relationship for constant pressure: \(\frac{V_1}{T_1} = \frac{V_2}{T_2}\), where \(V\) is volume and \(T\) is temperature in Kelvin.
4. Since pressure and the amount of gas (mass) remain constant, use the direct proportionality between volume and temperature to analyze how volume changes as temperature increases.
5. Conclude that because temperature increases (in Kelvin), the volume must increase proportionally, according to the ideal gas law.