Surface Chemistry

Methylene blue solution

(1) $\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11 \text { (aq) }}+\mathrm{H}_{2} \mathrm{O} \stackrel{\mathrm{H}^{+}}{\longrightarrow} \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6(\text { aq) }}+\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6(\text { aq )}}$ (Homogeneous reaction)

(2) $2 \mathrm{O}_{3(\mathrm{g})} \stackrel{\mathrm{NO}(\mathrm{g})}{\longrightarrow} 3 \mathrm{O}_{2(\mathrm{g})}$ (Homogeneous reaction)

(3) $\mathrm{N}_{2(g)}+3 \mathrm{H}_{2(\mathrm{g})} \stackrel{\mathrm{Fe}(\mathrm{s})}{\longrightarrow} 2 \mathrm{NH}_{3(\mathrm{g)}}$ (Reactants and catalyst are in different phase) It is heterogeneous reaction

(4) $\mathrm{SO}_{2(\operatorname{g)}}+\frac{1}{2} \mathrm{O}_{2(\mathrm{g})} \stackrel{\mathrm{NO}_{(g)}}{\longrightarrow} \mathrm{SO}_{3(\mathrm{g})}$

Pumice stone is an example of solid state

With increase in temperature, extent of adsorption $\left( {i.e.\,{x \over m}} \right)$ decreases so correct order of temperatures will be ${T_3} > {T_2} > {T_1}$

According to hardy Schulze rule

$\bullet$ Flocculating power of cation increases with increases in charge on cation of electrolyte in case of negatively charge colloid, hence order is

Al³⁺ > Ba²⁺ > Na⁺

$\bullet$ Flocculating power of anion increases with increases in charge on anion of electrolyte in case of positively charge colloids

Hence order is

NaCl < Na₂SO₄ < Na₃PO₄

Due to surface tension, liquid tends to have a minimum surface area. For a given volume of a liquid, sphere has the minimum surface area. Therefore, the small drops of liquids are spherical on flat surfaces, the droplets get slightly flatlended by the effect of gravity. Thus, both assertion and reason are correct and given reason is the correct explanation for the assertion.

When KI solution is added to $\mathrm{AgNO}_3$ solution, positively charged solution results due to adsorption of $\mathrm{Ag}^{+}$ from dispersion medium forming $\mathrm{AgI} / \mathrm{Ag}^{+}$ having acquired a positive charge, this layer attracts counter ions from the medium forming a second layer as $\mathrm{AgI} / \mathrm{Ag}^{+}: \mathrm{I}^{-}$.

Both assertion and reason are true but reason is not the correct explanation of assertion.

At a certain concentration, surfactant molecules start to aggregate and from micelle. This concentration is called critical micellar concentration (CMC).

Aggregation of surfactant molecules (ions; RCOO$^-$), i.e. micelle formation causes effective fall in number of free ions to conduct electricity, thus conductivity decreases at CMC.