Question

An evacuated glass vessel weights 50.0 g when empty. 148.0 gm when filled with a liquid of density 0.98 g/mL and 50.5 g when filled with an ideal gas at 760 mm Hg at 300 K. Determine the molecular weight of the gas.

• A. 125
• B. 141
• C. 152
• D. none of these

Answer 1

The correct option is A 125

mass of containers $=50g$

$\therefore$ mass of liquid $=(148-50)$

$=98g$

$density=0.98g/mL$

$V=\frac{m}{d}$

$=\frac{98}{0.98}\times 100$

$=100mL$

$=0.1mL$

mass of gas $=(50.5-50)g$

$=0.5g$

$\Rightarrow P=760mm$ of $Hg=1atm$

$T=300K$

$\therefore PV=nRT$

$1\times 0.1=n\times \frac{1}{12}\times 300$

$n\times 25=0.1$

$n=\frac{0.1}{250}$

$n=0.004$

$\therefore$ mass of $0.004mole=0.5g$

$\therefore$ mass of $0.004mole=\frac{0.5\times 1000}{4}$

$=125g$