Surface chemistry practice · Mixed difficulty

Option A (Cellulose nitrate in a alcohol-ether) is correct because collodion is a solution of cellulose nitrate in a mixture of alcohol and ether, used for various applications including preparing ultrafilters.

Option B (Combustion of coal) is correct because it doesn't involve a catalyst, unlike the other options which are heterogeneous catalytic reactions.

Option B ($\Delta H$ is of the order of 40 KJ) is correct because the enthalpy change for chemisorption is typically much larger than 40 kJ/mol.

Option B (${\mathrm{C}_2}{\mathrm{H}_5}\mathrm{OH}$) is correct because ethanol (${\mathrm{C}_2}{\mathrm{H}_5}\mathrm{OH}$) acts as a negative catalyst to retard the oxidation of chloroform, preventing the formation of phosgene.

Option A (May be defined as the milligram of the dry material of which the hydrophilic sol is prepared and which when added to 10 mL of red gold sol, will prevent it from coagulation on the addition of 1 mL of 10 per cent sodium chloride solution) is correct because it accurately describes the definition of gold number.

Option D (${\left[ {Fe{{\left( {CN} \right)}_6}} \right]^{4 - }}$) is correct because according to the Hardy-Schulze rule, ions with higher charges are more effective in causing coagulation of colloids.

Option B ($\log \frac{X}{m} = \log k + \frac{1}{n}\log p$) is correct because the Freundlich adsorption isotherm is expressed as $\frac{X}{m} = k{p^{1/n}}$, which can be written in logarithmic form as $\log \frac{X}{m} = \log k + \frac{1}{n}\log p$.

Option C (Synthetic gems) is correct because synthetic gems are a solid dispersed in another solid, forming a solid-solid system.

Option C (Bredig’s Arc method) is correct because Bredig's arc method is a common method for preparing colloidal solutions of metals like gold.

Option B is correct. Peptisation is the process of converting a precipitate into a colloidal solution by shaking it with a dispersion medium in the presence of a small amount of electrolyte.

Option D (Zero activation energy) is correct because chemical adsorption involves the formation of chemical bonds, which requires a significant activation energy.

Option C (Solid dispersed in gas) is correct because smoke consists of solid particles (like carbon) dispersed within a gaseous medium (like air).

Option C (Size of particles) is correct because the efficiency of a catalyst is highly dependent on its surface area, which is related to the size of its particles.

Option B (ZSM-5) is correct because ZSM-5 is a zeolite catalyst used to convert alcohols directly into gasoline in petrochemical industries.

Option B is correct. Adsorption is a spontaneous process (ΔG < 0) that results in a decrease in entropy (ΔS < 0) and is exothermic (ΔH < 0).

Option C (Viscosity is of the order of that of water) is the false statement because hydrophilic sols have a much higher viscosity than water.

Option B is correct. A catalyst in finely divided form has a larger surface area, leading to more active sites where reactions can occur.

Option B (physical adsorption in general increases with temperature) is wrong because physical adsorption decreases with increasing temperature due to the weak van der Waals forces involved.

Option C (Hydrogenation of oils requires iron as catalyst) is correct because hydrogenation of oils typically uses nickel (Ni) as a catalyst, not iron.

Option C ($\mathrm{SO}_2$) is correct because readily liquefiable gases like sulfur dioxide are more easily adsorbed by activated charcoal due to stronger van der Waals forces.

Option A (Heterogeneous catalyst) is correct because the catalyst (platinized asbestos) is in a different phase (solid) than the reactants (gases).

Option B (Viscosity and surface tension are equal to that of water) is not a property of hydrophilic sols because hydrophilic sols have higher viscosity and lower surface tension than water.

Option C (Starch aqueous solution) is correct because starch readily forms a colloidal solution in water, exhibiting lyophilic properties.

Option A (Low T, high P) is correct because physical adsorption is an exothermic process favored by low temperature and high pressure according to Le Chatelier's principle.

Option B (Sulphur sol) is correct because Sulphur sol is formed by the aggregation of a large number of sulphur molecules, making it a multimolecular colloid.

Option B is correct because the Hardy-Schulze rule states that ions with higher charges are more effective in coagulating colloids with opposite charges.

Option A (Dialysis) is correct because dialysis is a process that separates small molecules from larger ones in a solution, and it is used to purify blood by removing waste products.

Option A (Liquid in liquid) is correct because an emulsion is a colloidal dispersion of one liquid in another immiscible liquid.

Option B is correct because protective power is inversely proportional to the gold number, so the substance with the lowest gold number has the highest protective power.

Option C (Non-specificity) is correct because physisorption involves weak van der Waals forces, which are universal and do not show preference for a particular gas.