250 mL of hydrogen is collected over water at 27 degC and a total pressure of 740 mm Hg. The aqueous tension (vapour pressure of water) at 27 degC is 20 mm Hg. Taking R = 0.0821 L atm K^-1 mol^-1, the amount of dry hydrogen in millimoles (one decimal) is

JEE Main levelNumerical answerDifficulty 2 of 3ig027

$250 mL$ of hydrogen is collected over water at $2 7^{\circ} C$ and a total pressure of $740 mm Hg$ . The aqueous tension (vapour pressure of water) at $2 7^{\circ} C$ is $20 mm Hg$ . Taking $R = 0.0821 L atm K^{- 1} mo l^{- 1}$ , the amount of dry hydrogen in millimoles (one decimal) is

Numerical answer type, answer in mmol, tolerance 0.1.

Pressure of dry

H X_{2}

= 740 - 20 = 720 mm Hg = 720/760 atm

n = \frac{P V}{RT} = \frac{( 720/760 ) \times 0.250}{0.0821 \times 300} = 0.00962 mol \approx 9.6 mmol