Question

Volume of a gas at NTP is $1.12\times {10}^{-7}$ cm${}^{-3}$. Calculate the number of molecules in it.

• A. $3.01\times {10}^{12}$
• B. $3.01\times {10}^{20}$
• C. $3.01\times {10}^{24}$
• D. $3.01\times {10}^{23}$

Answer 1

The correct option is A $3.01\times {10}^{12}$

$22400$ cm${}^{-3}$ of gas at NTP corresponds to 1 mole or $6.02\times {10}^{23}$ molecules (Avogadro's number).

$1.12\times {10}^{-7}$ cm${}^{-3}$ of gas has $=\frac{6.02\times {10}^{23}}{22400}\times 1.12\times {10}^{-7}=3.01\times {10}^{12}$ molecules.

Hence, the correct option is $A$