Problem 179
Assertion: Coagulation power of \(\mathrm{Al}^{3}\) is more than \(\mathrm{Na}\). Reason: Greater the valency of the flocculating ion added greater is its power incause precipitation (Hardy Schulze rule).
Problem 180
Assertion: Detergents with low CMC are more economical to use Reason: Cleansing action of detergents involves the formation of micelles. These are formed when the concentration of detergents becomes equal to CMC.
Problem 182
How many of these solutions are colloid here? Butter, Smoke, Pumic stone, milk, sugar solution, Aq solution of \(\mathrm{C}_{2} \mathrm{H}_{5}\) OH Ruby glass, cold cream, Paints.
Problem 184
How many of these metals are usally used as catalysts Pd, \(\mathrm{Pt}, \mathrm{Ni}, \mathrm{Na} / \mathrm{liq} \cdot \mathrm{NH}_{3}\)
Problem 185
Alum is widely used to purify water since \(\quad\) (a) it forms complex with clay particles (b) it coagulates the mud particles (c) it exchanges \(\mathrm{Ca}^{2+}\) and \(\mathrm{Mg}^{2+}\) ions present in hard water (d) its sulphate ion is water purifier
Problem 186
Which of the following characteristics is not correct for physical adsorption? (a) adsorption on solids is reversible (b) adsorption is spontaneous (c) both enthalpy and entropy of adsorption are negative (d) adsorption increases with increase in temperature
Problem 187
Identify the correct statement regarding enzymes. (a) Enzymes are specific biological catalysts that cannot be poisoned (b) Enzymes are specific biological catalysts that possess well defined active sites (c) Enzymes are specific biological catalysts than can normally function at very high temperatures (1000\textrm{K} ) ~ (d) Enzymes are normally heterogeneous
Problem 188
Which of the following is adsorbed in maximum amount by activated charcoal? (a) \(\mathrm{N}_{2}\) (b) \(\mathrm{CO}\) (c) \(\mathrm{NHCl}\) (d) \(\mathrm{CO}_{2}\)
Problem 190
The disperse phase in colloidal iron (III) hydroxide and colloidal gold is positively and negatively charged, respectively. which of the following statements is incorrect? (a) magnesium chloride solution coagulates, the gold sol more readily than the iron (III) hydroxide sol (b) sodium sulphate solution causes coagulation in both sols (c) mixing of the sols has no effect (d) coagulation in both sols can be brought about by electrophoresis
Problem 191
In Langmuir's model of adsorption of a gas on a solid surface (a) the rate of dissociation of adsorbed molecules from the surface does not depend on the surface covered (b) the adsorption at a single site on the surface may involve multiple molecules at the same time (c) the mass of gas striking a given area of surface is proportional to the pressure of the gas (d) the mass of gas striking a given area of surface is independent of the pressure of the gas
