Question

A plant virus is found to consist of uniform symmetrical particles of 150 $\stackrel{o}{A}$ in diameter and 5000 $\stackrel{o}{A}$ long. The specific volume of the virus is 0.75 $c{m}^3/g$. The virus is considered to be a single particle. If its molecular weight is $x\times {10}^7$, find x.

Answer 1

Volume of each particle = $\frac{1}{4}\pi d^{2}l=0.25\times 3.14\times 225\times {10}^{-20}\times 50\times {10}^{-10}c{m}^3=8.83\times {10}^{-27}c{m}^3$

Mass of each virus = $\frac{volume}{specificvolume}=\frac{8.83\times {10}^{-27}}{0.75}g=11.77\times {10}^{-27}g$

Molecular weight = $\frac{11.7\times {10}^{-27}}{1.66\times {10}^{-27}}=7.09$