Question

Calculate the total pressure in a $ 10.0\, L $ cylinder which contains $ 0.4 \,g $ helium, $ 1.6 \,g $ oxygen and $ 1.4\, g $ nitrogen at $ 27^{\circ}C $ .

• A. $ 0.492 $ atm
• B. $ 49.2 $ atm
• C. $ 4.92 $ atm
• D. $ 0.0492 $ atm

Answer 1

Answer: (A)

Number of mol of $He = \frac{0.4}{4} = 0 .1 $
Number of mol of oxygen $ = \frac{1.6}{32} = 0 . 05$
Number of mol of nitrogen $ =\frac{1.4}{28} = 0. 05 $
Total moles in the $10.0\,L$ cylinder at
$27^{\circ} = ( 0.1 + 0.05) + 0. 05^{\circ}$
$ = 0. 2\, mol$
$P_T = \frac {nRT}{V} $
$ = \frac{0.2 × 0.082 ×300}{10}$
$ = 0 . 492 \, atm$