Question

32. If 3.011 1022 molecules of a diatomic gas weigh
3.55 g then molar mass of the gas is
(1) 35.5 g/mol (2) 71 g/mol
2 (3) 142 g/mol (4) 177.5 g/mol
​

Answer 1

3.011x10^22 molecules =3.55 gm

6x10^23 molecules =?

6x10^23 x 3.55 / 3.011x 10^22

=71 g/mol

Answer 2

The molar mass of the gas is 71 g/mol

GIVEN

Weight of 3.011 × 10²² molecules of a diatomic gas = 3.55 grams

TO FIND

Molar mass of the gas

SOLUTION

We can simply solve the above problem as follows;

We know that Molat mass of a substance = 6.022 × 10²³(Nₐ) molecules of the substance.

It is given,

Weight of 3.022 × 10²² molecules of gas = 3.55 grams

So,

weight of 1 molecule = 3.55/3.022 × 10²² = 1.17 × 10⁻²³ grams

Weight of Nₐ molecules of gas = 1.17 × 10⁻²³ × 6.022 × 10²³

= 7.045 × 10

=70.45 ~ 71 grams

Hence, The molar mass of the gas is 71 g/mol

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