Equilibrium practice · Easy

Option A (0.208) is correct because it is calculated using the equilibrium constant expression with the given concentrations.

Option C (Both S and E are correct and E is correct explanation for S) is correct because the acidic nature of cations increases with increasing effective nuclear charge.

Option A (Monobasic and weak Lewis acid) is correct because ${\mathrm{H}_3}\mathrm{B}{\mathrm{O}_3}$ accepts hydroxide ions from water, acting as a weak Lewis acid and releasing a proton.

Option C (No effect) is correct because, according to Le Chatelier's principle, pressure changes have no effect on equilibrium when the number of moles of gaseous reactants equals the number of moles of gaseous products.

Option D (All of these) is correct because all the given mixtures (acetic acid/sodium acetate, ammonium chloride/ammonium hydroxide, and HCN/NaCN) are buffer solutions.

The correct answer is $10^{-11}$ because the dissociation constant is calculated using the formula $K_a = C \alpha^2$.

Option B is correct because sulfuric acid is a strong acid that almost completely ionizes in aqueous solution.

Option B (32.66) is correct because it is the equilibrium constant calculated from the given equilibrium concentrations using the equilibrium expression.

Option D (Remains unaffected) is correct because the addition of a solid reactant or product does not affect the equilibrium concentration of gaseous species in a heterogeneous equilibrium.

Option B (Alkaline) is correct because sodium bisulphite ($NaHSO_3$) forms bisulphite ions ($HSO_3^−$) in solution, which can act as a weak acid, but the hydrolysis of $SO_3^{2-}$ makes the solution alkaline.

Option C is correct. The assertion is true because K indicates the extent of a reaction. The reason is false because K is dependent on the stoichiometry of the balanced chemical equation.

Option C is correct because the pH of 1 × 10^-8 M HCl is not 8. Since HCl is an acid, the pH must be less than 7. The pH will be slightly less than 7 due to the contribution of H+ from water.

Option B (6.5) is incorrect, Option C (5.3) is the closest to the actual pH of ordinary water which is slightly acidic due to dissolved CO2, but Option A (7) is the pH of pure water, and Option D (7.8) is slightly alkaline. The correct answer is B (6.5)

Option A ($\mathrm{CH}_3^ -$) is correct because $\mathrm{CH}_3^ -$ is the conjugate base of the very weak acid $\mathrm{CH}_4$, making it the strongest base among the given options.

Option D (All of the above) is correct because all given mixtures can act as buffer solutions, either by containing a weak acid/base and its conjugate or by forming one upon reaction.

The correct answer is A (A low value for the equivalent weight) because methyl orange changes color at a lower pH than the equivalence point of a weak acid titration, leading to premature endpoint detection and an underestimation of the volume of titrant required, thus a lower calculated equivalent weight.

Option A (2.0) is correct because a lower $\mathrm{p}{K_a}$ value indicates a stronger acid.

Option B (0.0625) is correct because the equilibrium constant Kc is calculated by dividing the product concentration by the reactant concentrations, each raised to the power of their stoichiometric coefficients.

Option B (Pressure is decreased) is correct because decreasing pressure shifts the equilibrium to the side with more moles of gas, which is the reactants' side, thus decreasing ammonia yield.

Option B (${\mathrm{H}_3}{\mathrm{O}^ + }$) is correct because it can accept a pair of electrons due to the positive charge, making it a Lewis acid.

Option B is correct because the hydrolysis constant ${K_h}$ is inversely proportional to the product of the dissociation constants of the weak acid (${K_a}$) and weak base (${K_b}$).

The correct answer is D ($0.05\;\mathrm{M }\;\mathrm{N}{\mathrm{H}_3}$) because the solubility of $Ag_2CO_3$ is greatest in $NH_3$ due to complex formation, which reduces the concentration of $Ag^+$ ions.

Option D (5.1) is correct because $NH_4Cl$ is a salt of a weak base and a strong acid, which hydrolyzes to produce an acidic solution, resulting in a pH less than 7.

Option B ($4 \times 10^{-6}$) is correct because since Δn = 0, Kp = Kc.

Option A (The condition for equilibrium is ${\mathrm{G}_{{\mathrm{N}_2}}} + 3{\mathrm{G}_{{\mathrm{H}_2}}} = 2{\mathrm{G}_{\mathrm{N}{\mathrm{H}_3}}}$, where $\mathrm{G}$ is Gibbs energy per mole of gaseous species measured at that partial pressure) is correct because at equilibrium, the change in Gibbs free energy is zero, meaning the Gibbs free energy of the reactants equals the Gibbs free energy of the products.

Option C (Remains unaffected) is correct because the addition of a solid reactant or product does not change the equilibrium constant, which depends only on the partial pressure of CO2 in this case.

Option D ($\frac{{1}}{{{{RT}}}}$) is correct because it is derived from the relationship between Kp and Kc, considering the change in the number of moles.

Option A (atm) is correct because the units of Kp depend on the difference in the stoichiometric coefficients of gaseous products and reactants.

Option B ($\frac{1}{{{K_1}{K_2}}}$) is correct because the reaction is the reverse of the sum of the reactions with equilibrium constants K1 and K2.

Option D (None of these) is correct because the normality depends on the acid's nature (strong or weak) and its dissociation.