Surface chemistry practice · Mixed difficulty

Option D (Sugar solution) is correct because sugar solution is a true solution and does not scatter light, therefore it does not show the Tyndall effect.

Option A (Starch solution) is correct because the Tyndall effect is exhibited by colloidal solutions, and starch solution is a colloid.

Option A (Adsorbate) is correct because the adsorbate is the substance that adheres to the surface of the adsorbent during adsorption.

Option D (Chorcoal) is correct because charcoal is a good adsorbent and can adsorb methylene blue dye, causing it to become colorless.

Option A (Oxidation of ammonia to form nitric acid) is correct because Platinum acts as a catalyst in the Ostwald process for the oxidation of ammonia to nitric oxide, which is a precursor to nitric acid.

Option A ($\mathrm{KCl}$) is correct because it has the lowest charge among the given electrolytes, thus requiring a higher concentration to cause coagulation of the negatively charged $\mathrm{As}_2 \mathrm{S}_3$ sol.

Option A (Glucose) is correct because the hydrolysis of maltose by maltase yields two molecules of glucose.

Option D (5 g) is correct because it is the amount of solute adsorbed per gram of adsorbent calculated using the Freundlich adsorption isotherm equation with the given parameters.

Option D (250) is correct because the gold number is the mass in milligrams of the protective colloid that prevents coagulation.

Option A (Gel formation) is correct because cementation involves the formation of a gel-like structure as water molecules are held within the cement particles.

Option B is correct because a liquid dispersed in a solid is called a gel, not a solid foam. Solid foam has a gas dispersed in a solid.

Option D ($NaCl$ Solution) is correct because $NaCl$ solution is a true solution, where the solute particles are too small to scatter light and exhibit the Tyndall effect.

Option D (Latex is a colloidal solution of rubber particles which are positively charged) is the false statement because latex particles are negatively charged, not positively charged.

Option C is correct because in an aerosol, the dispersion medium is a gas, and the dispersed phase can be either solid or liquid.

Option A (Saliva) is correct because ptyalin (salivary amylase) is an enzyme present in saliva used for the digestion of food.

Option C ($2.1 \mathrm{L} \mathrm{g}^{-1}$) is correct because it is calculated by finding the volume of oxygen adsorbed per gram of adsorbent using the ideal gas law.

Option B (1) is correct because 1 mole of lead nitrate ($Pb^{2+}$) is required to coagulate 2 moles of colloidal $[AgI]I^-$.

Option C is correct. The assertion about chemisorption increasing with temperature initially and then decreasing is correct, but the reason that heat keeps providing more activation energy is incorrect. After reaching a certain temperature, the kinetic energy of the adsorbate becomes too high, leading to desorption.

Option B (Formaldehyde solution) is correct because formaldehyde acts as a preservative for milk by inhibiting bacterial growth.

Option D (All of the above) is correct because all the given statements accurately describe the characteristics of zeolites.

Option A ($\frac{x}{m} = K{p^{0.3}}$) is correct because the Freundlich adsorption isotherm is represented by $\frac{x}{m} = K{p^{1/n}}$, where 0 < 1/n < 1. 0.3 falls within this range.

The correct answer is A (Methylene blue) because basic dye stuffs like methylene blue form positive sols.

Option A (Aerosol) is correct because a colloidal system of solid in gas is defined as an aerosol.

Option B (Pt) is correct because platinum (Pt) is used as a catalyst in the Ostwald process for the manufacture of nitric acid.

Option B (Sol A is positively charged and Sol B is negatively charged) is correct because a lower flocculation value for BaCl2 compared to KCl indicates that sol A is negatively charged and a lower flocculation value for Na2SO4 compared to NaBr indicates that sol B is positively charged.

The correct answer is D (Negatively as well as positively charged particles) because blood contains both positively and negatively charged ions, but its overall charge is considered negative due to the presence of negatively charged proteins.

Option D is correct because, according to the Freundlich adsorption isotherm, the slope of the plot of $\log \frac{x}{m}$ vs $\log p$ is equal to $\frac{1}{n}$.

Option A (${Ba}^{2+}, 1.0$) is correct because the flocculating value is determined by the concentration of the effective ion (${Ba}^{2+}$) required for coagulation.

Option C (S-I is false & S-II is true) is correct because cod liver oil is a water-in-oil emulsion, not oil-in-water.

Option D (Clouds) is correct because clouds are aerosols, not emulsions. Emulsions have both dispersed phase and dispersion medium in liquid state.