Question

Suppose the chemists hed selected ${10}^{20}$ as the number of particles in a mole. The molar mass of oxygen gas would be (Use Avogadro number $=6.0\times {10}^{23}$)

• A. $5.33\times {10}^{-3}g$
• B. $5.35\times {10}^{-23}g$
• C. $5.33\times {10}^{-43}g$
• D. $32\times {10}^{3}g$

Answer 1

Answer: (A)

$5.33\times {10}^{-3}g$

Molar mass of oxygen we know is $32$g.

$\therefore 1$ molecule oxygen weighs $\frac{32}{6\times {10}^{23}}$g

$\Rightarrow {10}^{20}$ molecules would weigh $\frac{32}{6\times {10}^{23}}\times {10}^{20}$

$\therefore 1$mole would weigh $=5.33\times {10}^{-3}$g.