Question

A detergent $C_{12}{H}_{25}S{O}_4^{-}N{a}^{+}$ solution becomes a colloidal sol at a concentration of ${10}^{-3}M$. On an average ${10}^{13}$ colloidal particles are present in $1m{m}^3$. What is the average number of ions which are contained in one colloidal particle (micelle) ? [GIven : $N_A=6\times {10}^{23}$]

• A. $6\times {10}^7$
• B. $10$
• C. $60$
• D. none of these

Answer 1

The correct option is C $60$

No. of sodium lauryl sulphate $\left(C{H}_3\right(C{H}_2{)}_{11}S{O}_4^{-}N{a}^{+})$ in $1$ litre solution
$={10}^{-3}\times 6\times {10}^{23}$
$=6\times {10}^{20}$
No. of sodium lauryl sulphate per $m{m}^3=6\times {10}^{14}$
No. of colloidal particles per $m{m}^3={10}^{13}$
No. of molecular per colloidal particle
$=\frac{6\times {10}^{14}}{{10}^{13}}$
$=60$