Question

Two identical vessels seperately contain equal masses of hydrogen gas and helium at the same temperature. Then:

• A. the number of molecules in the two vessels are equal
• B. the pressures are equal
• C. the pressure of hydrogen is double of that of helium
• D. the pressure of hydrogen is half of that of helium

Answer 1

Answer: (C)

the pressure of hydrogen is double of that of helium

For hydrogen gas($H_2$),

$P_{H}V=\frac{w}{M_H}RT$

Similarly, for helium($He$),

$P_{He}V=\frac{w}{M_{He}}RT$

According to question, at same temperature and volume,

$\frac{P_H}{P_{He}}=\frac{M_{He}}{M_H}$

$=\frac{4}{2}$

Therefore, $P_H=2P_{He}$

Hence, the correct answer is option $\text{C}$.