Surface Chemistry question bank (Chemistry)

$20 \mathrm{mL}$ of $0.5 \mathrm{M} \mathrm{NaCl}$ is required to coagulate $200 \mathrm{mL}$ of ${\mathrm{As}}_2{\mathrm{S}}_3$ solution in $2$ hours. The coagulating value of $\mathrm{NaCl}$ is ___________.

Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R.

Assertion A : The diameter of colloidal particles in solution should not be much smaller than wavelength of light to show Tyndall effect.

Reason R : The light scatters in all directions when the size of particles is large enough.

In the light of the above statements, choose the correct answer from the options given below :