Question

A cylinder of fixed capacity \( 67.2 \, \mathrm{L} \) contains helium gas at STP. The amount of heat needed to raise the temperature of the gas in the cylinder by \( 20^\circ \mathrm{C} \) is:

• A. \( 700.5 \, \mathrm{J} \)
• B. \( 747.9 \, \mathrm{J} \)
• C. \( 760.2 \, \mathrm{J} \)
• D. \( 800.0 \, \mathrm{J} \)

Hint:

For monatomic gases like helium, \( C_v = \frac{3}{2} R \) and \( C_p = \frac{5}{2} R \). Use \( Q = n C_v \Delta T \) for calculations at constant volume.