Question

DNA has density $1.1$ g/mL and its molecular weight is $6\times {10}^3$ g/mol. Average volume occupied by its single molecule will be:

• A. $9.1\times {10}^{-20}$ cc
• B. $9.1\times {10}^{-21}$ cc
• C. $9.8\times {10}^{-21}$ cc
• D. $9.6\times {10}^{-20}$ cc

Answer 1

The correct option is B $9.1\times {10}^{-21}$ cc

$1$ mole of DNA weighs $6000$ g and its volume is $V=\frac{M}{D}=\frac{6000}{1.1}=5455$ cc.
This is the volume occupied by $6.023\times {10}^{23}$ molecules.
The volume occupied by $1$ molecule will be $\frac{5455}{6.023\times {10}^{23}}=9.1\times {10}^{-21}$ cc.