Question

3.01 x 10${}^{21}$ molecules of a gas weigh 1.7gm. The molecular weight of gas is:

• A. $170$
• B. $340$
• C. $17$
• D. $85$

Answer 1

The correct option is B $340$

We know that,

weight of $6.023\times {10}^{23}$ molecules = molecular weight

given, weight of $3.01\times {10}^{21}$ molecules = 1.7gm

so, weight of $6.023\times {10}^{23}$ molecules = $\frac{1.7}{3.01\times {10}^{21}}\times 6.023\times {10}^{23}=340$

so, molecular weight of gas = 340
Option B is correct.