Question

$50$ $c{m}^3$ of hydrogen is collected over water at ${17}^o$C and $750$ mm Hg pressure. Calculate the volume of dry gas at S.T.P.

[The water vapour pressure at ${17}^o$C is $14$ mm Hg.]

• A. $55.58c{m}^3$
• B. $45.58c{m}^3$
• C. $35.58c{m}^3$
• D. $65.58c{m}^3$

Answer 1

Answer: (B)

$45.58c{m}^3$

Given that

$P_1=750mmHg-14mmHg=736mmHg$

$V_1=50c{m}^3,T_1={17}^{0}C=290K$

$P_2=760mmHg$

$V_2=?c{m}^3,T_2=0^{0}C=273K$

Hence the Gas equation

$\frac{P_1{V}_1}{T_1}=\frac{P_2{V}_2}{T_2}$

$\frac{736\times 50}{290}=\frac{760\times V_2}{273}$

$\therefore V_2=\frac{736\times 50\times 273}{290\times 760}$

$V_2=45.58c{m}^3$

Thus, the volume of dry gas at STP is $45.58c{m}^3$

Hence, the correct option is $B$