Question

Volume of gas at STP is $1.12\times {10}^{-7}cc$. Calculate the number of a molecule in it.

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

Answer 1

Answer: (B)

At STP, mole of gas occupies $22400cc$.
mole of gas occupies $1.12\times {10}^{-7}cc$
$=\frac{1.12\times {10}^{-7}}{22400}\times 1=5\times {10}^{-12}moles$
1 mole of any gas contains
$=6.022\times {10}^{23}molecules$
$5\times {10}^{-12}moles$ contains
$=5\times {10}^{-12}\times 6.022\times {10}^{23}molecules$
$=3.011\times {10}^{12}molecule$