Equilibrium · Question 79

A weak acid, HA, has a Ka of 1.00 10-5. If 0.100 mol of this acid is dissolved in one litre of water, the percentage of acid dissociated at equilibrium is closest to

1. 1.00\%
2. 99.9\%
3. 0.100\%
4. 99.0\%

Calculate the pOH of a solution at 25 C that contains 1 10-10 M of hydronium ions, i.e. H3O+.

1. 4.000
2. 9.000
3. 1.000
4. 7.000

For the reaction : CH4(g) + 2O2(g) CO2(g) + 2H2O(l), Hr = -890.3 kJ mol-1. Which of the following statements is not true?

1. The reaction is exothermic.
2. At equilibrium, the concentrations of CO2(g) and H2O(l) are not equal.
3. The equilibrium constant for the reaction is given by Kp = [CO2][CH4][O2]
4. Addition of CH4(g) or O2(g) at equilibrium will cause a shift to the right.

Which of the following pairs constitutes a buffer?

1. HCl and KCl
2. HNO2 and NaNO2
3. NaOH and NaCl
4. HNO3 and NH4NO3

The hydrogen ion concentration of a 10-8 M, HCl aqueous solution at 298 K (Kw = 10-14) is

1. 1.0 10-8 M
2. 1.0 10-6 M
3. 1.0512 10-7 M
4. 9.512 10-8 M

At 25 , the dissociation constant of a base, BOH, is 1.0 10-12. The concentration of hydroxyl ions in 0.01 M aqueous solution of the base would be

1. 1.0 10-5 mol L-1
2. 1.0 10-6 mol L-1
3. 2.0 10-6 mol L-1
4. 1.0 10-7 mol L-1

H2S gas when passed through a solution of cations containing HCl precipitates the cations of second group of qualitative analysis but not those belonging to the fourth group. It is because

1. presence of HCl decreases the sulphide ion concentration
2. solubility product of group II sulphides is more than that of group IV sulphides
3. presence of HCl increases the sulphide ion concentration
4. sulphides of group IV cations are unstable in HCl.

Equilibrium constants K1 and K2 for the following equilibria: NO(g) + 12O2(g) K1 NO2(g) and 2NO2(g) K2 2NO(g) + O2(g) are related as

1. K2 = 1/K12
2. K2 = K12
3. K2 = 1/K1
4. K2 = K1/2

The solubility product of a sparingly soluble salt AX2 is 3.2 10-11. Its solubility (in moles/L) is

1. 5.6 10-6
2. 3.1 10-4
3. 2 10-4
4. 4 10-4

The rapid change of pH near the stoichiometric point of an acid-base titration is the basis of indicator detection. pH of the solution is related to ratio of the concentrations of the conjugate acid (HIn) and base (In-) forms of the indicator by the expression

1. [In-][HIn] = pKIn - pH
2. [HIn][In-] = pKIn - pH
3. [HIn][In-] = pH - pKIn
4. [In-][HIn] = pH - pKIn