Question

0.157 g of a certain gas collected over water occupied a volume of 135 ml at ${27}^{0}C$ and 750 mm of Hg. Assuming ideal behaviour, the molecular weight of the gas is (aqueous tension at ${27}^{0}C$ is 26.7 mm of Hg)

• A. 30
• B. 32
• C. 28
• D. 16

Answer 1

The correct option is A

30

$P_{gas}=P_{water}-aq.tension$
= 750-26.7=723.3 atm
$PV=\frac{W}{M}RT$
$M=\frac{WRT}{PV}=\frac{0.157\times 0.0821\times 300}{723.3\times \frac{135}{100}}$
$M=30$