Ionic Equilibrium - 1
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Transcript of Ionic Equilibrium - 1
ANDHERI / VILE PARLE / DADAR / CHEMBUR / THANE / CHURCHGATE / NERUL / POWAI
Ionic Equilibrium
1. Account for the acidic properties of nirocus acid in terms of
(i) Arrhenius theory and (ii) Bronsted Lowry theory
2. Write a balanced equation for the dissociation of each of the following Bronsted Lowry acids in water.
(a) H2SO4 (b) H3O+ (c) HSO 4
-
3. Which of the following reactions proceeds to the right and which proceeds to the left if you mix equal
concentrations of reactants andproducts?
(a) HF(aq) + NO 3
- (aq) ˆ ˆ ˆ†‡ ˆ ˆˆ HNO3(aq) + F(aq)
(b) NH 4
+ (aq) + CO 2
3
- (aq) ˆ ˆ ˆ†‡ ˆ ˆˆ HCO 3
- (aq) + NH3(aq)
4. What are conjugate base of each of the following Bronsted Lowry acid?
(a) HNO2 (b) HNO 2
4
- (c) H2O (d) CH3NH 3
+
(e) H2CO3 (f) H2 (g) H2O2 (h) HO 2
-
5. Which of the following species behave as a strong acids or as strong base in aqueous solutions?
(a) HNO2 (b) HNO3 (c) NH+ (d) Cl
(e) H
(f) O2
(g) H2SO4
6. Justify the statement by giving example that Lewis base is also Bronsted Lowry base and vice – versa.
Is this statement true for Lewis acid?
7. Kb for trimethylamine is 6.5 105
. Calculate Ka for trimethyl ammonium ion (CH3)3 NH+
8. For the following equilibrium: NH3 + H2O ˆ ˆ ˆ†‡ ˆ ˆˆ NH4+ + OH
calculate equilibrium constant, if for
the equilibrium, NH4+ + H2O ˆ ˆ †̂‡ ˆ ˆˆ NH4OH + H
+ equilibrium constant is 5.55 10
10
9. CO2 in aqueous solution shows following ionic equilibrium:
2H2O + CO2 ˆ ˆ ˆ†‡ ˆ ˆˆ HCO 3
- + H3O+
If hydronium ion (H3O+) concentration, is 2 10
6 M, what is hydroxide ion (OH
) concentration?
10. If equilibrium constant of (I)
CH3COO + H2O ˆ ˆ †̂‡ ˆ ˆˆ CH3COOH + OH
(I) is 5.55 10
10, calculate equilibrium constant of (II)
CH3COOH + H2O ˆ ˆ ˆ†‡ ˆ ˆˆ CH3COO
+ H3O
+ (II)
CH3COO + H2O ˆ ˆ †̂‡ ˆ ˆˆ CH3COOH + OH
(I)
CH3COOH + H2O ˆ ˆ ˆ†‡ ˆ ˆˆ CH3COO + H3O
+ (II)
11. A flask containing 0.50 atm of ammonia contains some solid NH4HS which undergoes dissociation
according to NH4HS(g) ˆ ˆ ˆ†‡ ˆ ˆˆ NH3(g). Calculate the pressure of NH3 and H2S at equilibrium (Kp =
0.11). Also, calculate the total pressure.
12. What is normality of the resulting solution (acid/basic/neutral) when following solution are mixed?
(I) 0.1 M H2SO4, (II) 0.1 M HCl, (III) 0.1 M Ca(OH)2 (IV) 0.1 M NaOH
(a) I and II, in 1:1 volume (b) I and II, in 1:2 volume
(c) I and IV, in 1:2 volume (d) I and III, in 1:1 volume
(e) II and III in 1:1 volume (f) II and III in 2:1 volume
(g) II and IV in 1:2 volume
13. Ka for HCN is 4.9 1010
, calculate Kb for CN
14. (a) pH of a solution is 10 in NaOH solution. What is concentration of NaOH?
(b) What is molar concentration of Ca(OH)2 if its solution has pH of 12?
15. Calculate pH of
(a) 102
M H2SO4 (b) 102
NH2SO4 (c) 102
M Ca (OH)2 (d) 102
NCa(OH)2
16. Calculate pH of each of the following solutions:
(a) a sample of seawater that has [OH] = 1.60 10
6 M
(b) a sample of acid rain that has [H3O+] = 6.0 10
6 M
(c) HCl solution of concentration 4 107
M
(d) 1 M HCl
(e) a solution of lime containing 0.56g CaO (lime) in 100 mL solution.
17. For which of the following solutions must we consider the ionization of water when calculating the pH
or pOH:
(a) 3 108
M HNO3 (b) 0.10 g HCl in 1.0L of solution
(c) 0.0080 g of NaOH in 0.5 L of solution (d) 1 107
M Ca (OH)2
18. When 0.10 mole of NH3 is dissolved in water to make 1.0 L solution, the solution is found to have
[OH] = 1.34 10
3 M. Calculate Kb for NH3.
19. Ka of CH3COOH is 1.8 105
, calculate for 0.02 M CH3COOH
(i) [H3O+] (ii) % ionization and (iii) pH
20. If 50% of CO2 converts to CO at the following equilibrium:
C(s) + CO2(g) ˆ ˆ ˆ†‡ ˆ ˆˆ 2CO (g) and the equilibrium pressure is 12 atm, calculate Kp.
21. The density of an equilibrium mixture of N2O4 and NO2 at 1 atm 348 K is 1.84 g/L. Calculate KC for
the equilibrium N2O4 (g) ˆ ˆ ˆ†‡ ˆ ˆˆ 2NO2(g)
22. For the gaseous reaction of XO with O2 to form XO2, the equilibrium constant at 398 K is 1.0 104
lit/mole. If 1.0 mole of XO and 2.0 mole of O2 are placed in a 1.0 L vessel and allowed to come to
equilibrium, what will be the equilibrium concentration of each of the species?
23. At a temperature under high pressure Kw(H2O) = 1010
, A solution of pH 5.4 under these conditions is
said to be
(a) acidic (b) basic (c) neutral (d) amphitoric
24. 100 mL of 1 M HCl is mixed with 50 mL of 2 M HCl. Hence, [H3O+] is:
(a) 1.00 M (b) 1.50 M (c) 1.33M (d) 3.00 M
25. Consider following reactions:
(a) H2CO3(aq) + HSO 4
- (aq) ˆ ˆ ˆ†‡ ˆ ˆˆ H2SO4(aq) + HCO 3
- (aq)
(b) HF(aq) + Cl(aq) ˆ ˆ ˆ†‡ ˆ ˆˆ HCl(aq) + F
(aq)
(c) HF(aq) + NH3(aq) ˆ ˆ ˆ†‡ ˆ ˆˆ NH 4
+ + F(aq)
(d) HSO 4
- (aq) + CN(aq) ˆ ˆ ˆ†‡ ˆ ˆˆ HCN(aq) + SO 2
4
- (aq)
(a) a, b (b) c, d (c) a, c (d) b, d
26. If following proceed in forward side:
HNO2 + HF ˆ ˆ ˆ†‡ ˆ ˆˆ H2F+ + NO 2
-
CH3COOH + HF ˆ ˆ ˆ†‡ ˆ ˆˆ F + CH3COOH 2
+
H2O + CH3COOH ˆ ˆ ˆ†‡ ˆ ˆˆ H3O+ + CH3COO
then increasing order of acid strength is:
(a) H2O < CH3COOH < HF < HNO2 (b) HNO2 < HF < CH3COOH < H2O
(c) HNO2 < HF < H2O < C?H3COOH (d) HNO2 < CH3COOH < HF < H2O
27. [Cl] in a mixture of 200 mL of 0.01 M HCl and 100 ml of 0.01 M BaCl 2 is:
(a) 0.01 m (b) 0.0133 M (c) 0.03 M (d) 0.02M
28. Blue litmus turns red in the following mixture of acid and base:
(a) 100 mL of 1 102
M H2SO4 + 100 mL of 1 102
M Ca (OH)2
(b) 100 mL of 1 102
M HCl + 100 mL of 1 102
M Ba (OH)2
(c) 100 mL of 1 10
2 M H2SO4 + 10 mL of 1 10
2 M NaOH
(d) 100 mL of 1 102
M HCl + 100 mL of 1 102
M NaOH
29. At 50oC autoprotolysis of NH3 gives [NH 4
+ ] = 1 1015
M hence, autoprotolysis constant of NH3 is:
(a) -151 × 10 (b) 1 1030
(c) 1 1015
(d) 2 1015
30. Two equilibrium are simultaneously existing in a vessel at 25oC
NO(g) + NO2(g) ˆ ˆ ˆ†‡ ˆ ˆˆ N2O3(g); 1pK (say)
2NO2(g) ˆ ˆ ˆ†‡ ˆ ˆˆ N2O4(g) 2pK = 8
If initially only NO and NO2 are present in a 3 : 5 mole ratio and the total pressure at equilibrium is 5.5
atm with the pressure of NO2 at 0.5 atm, calculate 1pK
31. While calculating the pH of 107
M HCl, we have taken into account the common ion effect of HCl on
water. Why did we not take the common ion effect of water on HCl?
32. pH of 108
N NaOH is:
(a) 8.0 (b) 6.0 (c) 6.98 (d) 7.02
33. Which has maximum pH?
(a) 0.01 MH2SO4 (b) 0.01 M HCl (c) 0.01 M Ca(OH)2 (d) 0.01 M NaOH
34. For the following equilibrium: NH3 + H2O ˆ ˆ ˆ†‡ ˆ ˆˆ NH 4
+ + OH
NH 4
+ H2O ˆ ˆ ˆ†‡ ˆ ˆˆ NH4OH + H
+, k =
5.55 1010
.
35. 102
mole of NaOH was added to 10 litre of water. The pH will change by
(a) 4 (b) 3 (c) 11 (d) 7
36. 16.6 mg of solid sliver chromate (molar mass = 332) when put into 500ml water, silver ion and
chromate ion are obtained. On adding more solid, the concentration of ions does not increase. If 100 mg
of solid is put into 2 litre water, then the amount of solid remained undissociated would be 16.6 mg.
(a) 33.6 mg (b) 3.36mg (c) 66.4 mg (d) 6.64 mg
37. A 0.0200 M acid is 30% dissociated. The equilibrium constant Ka for the acid is
(a) 1.6 103
(b) 2.57 103
(c) 3.6 103
(d) 1.5 103
38. How much water must be added to 300 mL of a 0.2 M solution of CH3COOH for the degree of
dissociation of the acid to double? (Assume Ka of acetic acid is of order of 105
M)
39. Following two equilibria are established on mixing two gases A2 and C.
(i) 3A2 (g) ˆ ˆ ˆ†‡ ˆ ˆˆ A6(g) Kp = 1.6 atm2
(ii) A2(g) + C(g) ˆ ˆ ˆ†‡ ˆ ˆˆ A2C (g)
If A2 and C are mixed in 2:1 molar ratio, calculate the equilibrium partial pressure of A2, C, A2 C and
Kp for the reaction (ii). Given that the total pressure to be 1.4 atm and partial pressure of A6 to be 0.2
atm at equilibrium.
40. Calculate the change in pH when a 0.1 M solution of CH3COOH in water at 25oC is diluted to a final
concentration of 0.01 M.
(a) + 0.5 (b) + 0.4 (c) + 0.7 (d) + 0.6
41. What is the pH of a 1 M solution of acetic acid? To what volume must one litre of this solution be
diluted so that the pH of the resulting solution will be twice the original value? Given : Ka = 1.8 105.
42. Calculate the equilibrium constant for the following reaction at 25oC
. CN
+ CH3COOH ˆ ˆ ˆ†‡ ˆ ˆˆ
CH3COO + HCN. Given, ratio of Ka of HCN and CH3CHOOH is 2.7 10
5.
43. Which of the following increase with dilution at a given temperature?
(a) pH of 103
M acetic acid solution (b) pH of 103
M aniline solution
(c) degree of dissociation of 103
M acetic acid (d) degree of dissociation of 103
aniline
44. Find the pH of a solution 6 105
M in hcn (Ka = 4.9 10-10
) and 4 104
M in HIO (Ka = 2.25 1011
)
at 25oC. Kw = 10
14
45. Calculate [H+] of a solution that contains 0.1 M HCOOH (Ka = 1.8 10
4) and 0.1 M HOCN (Ka = 3.2
104
)
46. A weak monobasic acid is ionsed to the extent of 2 per cent in decinormal solution. Calculate the
degree of ionization of this acid in N/50 solution.
47. 0.96 gm of HI were heated to attain equilibrium 2HI ƒ H2 + I2. The reaction mixture on titration
requires 15.7 ml of N/10 Hypo solution. Calculate the degree of dissociation of HI.
48. Does the pH of solution increases, decreases or remain same when you
(a) add NH4Cl(s) to 100 ml of 0.1 M NH3?
(b) add sodium acetate (s) to 50 ml of 0.015 M acetic acid?
(c) add NaCl(s) to 25 ml of 0.1 M NaOH?
49. Determine the [S2
] in a saturated (0.1 M) H2S solution to which enough HCl has been added to
produce a [H+] of 2 10
4. K1 = 10
7, K2 = 10
14.
50. Find the pH of the solution resulting when 50 ml of 0.20 HCl is mixed with 50 ml of 0.20 M acetic acid
Ka for the latter = 1.8 105
.
51. What is the concentration of acetic acid which can be added to 0.5 M formic acid so that the %
dissociation of neither acid is changed by the addition? Ka for acetic acid is 1.85 105
, Ka for formic
acid = 2.4 104
.
52. Which one of the following salts when added to water does not affect the pH of water?
(a) FeCl3 (b) Al2(SO4)3 (c) Na2CO3 (d) KNO3
53. For 1.8 1012
M aqueous solution of formic acid (Ka = 1.8 104
), which of the following will be true
at 25oC?
(a) [H+] = 1.8 10
8 M (b) [OH
] = 5.56 10
7 M
(c) KW = 1014
(d) [H+] = 10
7 M
54. If the dissociation constant of two weak acids HA1 & HA2 are K1 & K2, then the relative strengths of
HA1 to HA2 are given by:
(a) 1
2
K
K (b) 2
1
K
K (c) 1
2
K
K (d) 2
1
K
K
55. Which one is the correct expression below for the solution containing „n‟ number of weak acids?
(a) n
+ i
i = 1 i
KH ] =
C[ å (b)
n+
i i
i = 1
H ] = K C[ å (c) n
+
i i
i = 1
H ] = K C[ å (d) None of these
56. Concentration of CO2 in atmosphere is 100 ppm. If CO2 present in 106 litres of air is dissolved in 1 dm
3
water than calculate the approximate pH of the solution at 27oC. Consider 10
6 litre air registers 1 atm
pressure. Given 1aK = 10
7,
2aK = 1011
; log 2 = 0.3
(a) 6 (b) 5.6 (c) 3.2 (d) 4.8
57. Potassium Cyanide is the deadliest poison know. Calculate the percent hydrolysis in a 0.06 M solution
of KCN.
58. The pH value will be highest for the aqueous solution of
(a) NaCl (b) Na2CO3 (c) NH4Cl (d) NaHCO3
59. At infinite dilution, the percentage ionization of both strong and weak electrolytes is
(a) 1 % (b) 20% (c) 50% (d) 100%
60. Which of the following salts is alkaline in water?
(a) CuSO4.5H2O (b) K2SO4 (c) NaNO3 (d) Na2B4O7. 10H2O
61. Which of the following slats does not undergo hydrolysis?
(a) NH4NO3 (b) FeCl3. 6H2O (c) KCl (d) KCN
62. Which of the following salts undergoes anionic hydrolysis?
(a) CuSO4 (b) NH4Cl (c) FeCl3 (d) Na2CO3
Passage : 1
Read the following passage and answer the questions numbered 7 to 11. They have only one correct
option)
The pH { log [H+]} value for pure water is 7.0, whereas natural rainwater is weakly acidic. This is
caused by dissolution of atmospheric carbon dioxide. In many areas, however, rainwater is more acidic.
This has several causes some of which are natural and some of which derive from human activity. In
the atmosphere, sulphur dioxide and nitrogen monoxide are oxidized to sulphur trioxide and nitrogen
dioxide respectively, which react with water to give sulphuric acid and nitric acid. The resulting so-
called “acid rain” has an average pH of 4.5. Values as low as 1.7 have however, been measured.
SO2(aq) + H2O(l) ˆ ˆ †̂‡ ˆ ˆˆ HSO -
3 (aq) + H+(aq)
1
+ -
3 -2
a
2
[H ][HSO ]K = = 10 M
[SO ]
HSO -
3 (aq) ˆ ˆ ˆ†‡ ˆ ˆˆ SO 2-
3 (aq) + H+(aq)
2
2- +
2 -7
a -
3
[SO ][H ]K = = 10 M
[HSO ]and equilibrium
SO2(aq) + H2O(l) ˆ ˆ †̂‡ ˆ ˆˆ SO 2-
3 (aq) + 2H+(aq)
1 2
2- + 2
2 -9
a a a
2
[SO ][H ]K = = K × K = 10 M
[SO ]
Also for water H2O ˆ ˆ ˆ†‡ ˆ ˆˆ H+ + OH
KW = [OH
] = 10
14
Now answer the following questions (T = 300 K for all questions).
63. The solubility of sulphur dioxide gas is 24.63 litre in 1 litre of water at partial pressure of 1 atm. Then
the concentration of SO2 in water saturated with SO2 gas (the change in volume caused by dissolution
of SO2 may be ignored) (R = 0.0821 litre atm. mol1
K1
) is
(a) 1.2 M (b) 1 M (c) 0.5 M (d) 2M
64. The pH of 0.01 M aqueous solution of sodium sulphite will be:
(a) 8.5 (b) 9 (c) 4.5 (d) 9.5
65. The dominant equilibrium in an aqueous solution of sodium hydrogen sulphite is
2HSO 2-
3 (aq) ˆ ˆ ˆ†‡ ˆ ˆˆ SO2(aq) + SO 2-
3 (aq) + H2O(l)
The equilibrium constant for the above reaction is:
66. Bromine is added dropwise to a 0.01 M solution of SO2. All sulphur dioxide is oxidized to sulphate
(VI), excess of bromine is removed. Then which of the following balanced reactions represent the
redox change:
(a) 2SO2(aq) + Br2(aq) ¾ ¾® 2SO 2-
4 (aq) + 2Br(aq)
(b) SO2(aq) + 2H2O(l) + Br2(aq) ¾ ¾® SO 2-
4 (aq) + 2Br (aq) + 4H
+(aq)
(c) H2O(l) + SO2(aq) + Br2(aq) ¾ ¾® SO 2-
4 (aq) + 2Br (aq) + 2H
+(aq)
(d) 2SO2(aq) + 3Br2(aq) + 4H2O(l) ¾ ¾® 2SO 2-
4 (aq) + 6Br (aq) + 8H
+(aq)
67. In the above problem which of the following is correct:
(a) [H+] + [SO 2-
4 ] = 0.04 M (b) [H+] + [HSO -
4 ] = 0.04 M
(c) [SO 2-
4 ] + [HSO -
4 ] = 0.02 M (d) [SO 2-
4 ] + [HSO -
4 ] + [H+]= 0.07 M
68. Consider the equilibrium: P(g) + 2Q(g) R(g). When the reactions carried out at a certain
temperature, the equilibrium concentration of P and Q are 3 M and 4 M respectively. When the volume
of the vessel is doubled and the equilibrium is allowed to be reestablished, the concentration of Q is
found to be 3M. Find (a) KC (b) concentration of R at two equilibrium stages.
Passage – 1
A solution capable of maintaining its pH relatively constant, when either excess acid or excess base is
added, is said to be buffered. While it is not usually considered a buffered solution, a concentrated
solution. (102
M and higher) of a strong acid or strong base is buffered against large changes in pH
when acids or bases are added.
Buffered solution are usually those containing a weak acid and a salt of that weak acid or a weak base
and the salt of that weak base. For example a solution containing HAC and NaAC resists large changes
in pH when acid or alkali is added.
For a buffer solution Buffer capacity is defined as the number of moles of as strong acid or a strong
base that causes 1L of the buffer to undergo a 1 unit change in pH. Buffer capacity is maximum when
the molar ratio of the two components is unity and the buffer solution is considered good.
69. The least change in pH on adding 0.01 mol of HCl to 1 litre of conc. HCl solutions will be in case of
(a) 0.1 M HCl (b) 0.2 M HCl (c) 0.3 M HCl (d) 0.4 M HCl
70. Which solution is not a buffer solution?
(a) NaCN (2 mole) + HCl (1 mole) in 5 L (b) NaCN (1 mole) + HCl (1 mole) in 5 L
(c) NH3(2 mole) + HCl (1 mole) in 5 L (d) CH3COOH (2 mole) + KOH (1 mole) in 5 L
71. Which species has the lowest concentration in a solution prepared by mixing 0.1 mole each of HCN
and NaCN in 1 L solution? Ka (HCN) = 1010
(a) CN (b) HCN (c) H
+ (d) OH
72. Which is the best buffer? CH3COOH (pKa = 4.7) CH3COONa (M = 82) CH3COOH (M = 60)
(a) 8.2 g CH3COONa & 6g CH3COOH in 1 litre
(b) 8.2 g CH3COONa & 8.2 g CH3COOH in 10 litre
(c) 8.2 g CH3COONa & 6g CH3COOH in 2 litre
(d) 16.4 g CH3COONa & 12 g CH3COOH in 4 litre
73. How many mole of strong acid should be added to decreases pH by one unit
(a) 0.0102 (b) 0.02045 (c) 0.0409 (d) 0.115
74. A sample of water has a hardness expressed as 80 ppm of Ca2+
. This sample is passed through an ion
exchange column and the Ca2+
is replaced by H+. What is the pH of the water after it has been so
treated?
(a) 3 (b) 2.7 (c) 5.4 (d) 2.4
75. 0.1 M solution of 2 salts, NaX and NaY have pH 9 and 11 respectively. Both salts are of weak acid and
strong base. Which acis is stronger HX or HY? Also calculate their ionization constants.
76. Calculate the pH in a 0.1 M solution of NH4OCN. Ka(HOCN) = 3.3 104
, Kb(NH3) = 1.8 105
.
77. Acetic acid and propionic acid have Ka values 1.75 105
and 1.3 105
respectively at a certain
temperature. An equimolar solution of a mixture of the two acids is available. How are their ionized
fractions related to the Ka values.
(a) α 1.75
= ×1 - α 1.3 1 -
b
b
æ öæ ö ÷ç÷ç ÷÷ çç ÷÷ çç ÷÷ç çè ø è ø, where and are ionized fractions of the acids
(b) The ratio is unrelated of the acids
(c) The ratio is unrelated to the molarity
(d) The ratio is unrelated to the pH of the solution
78. p1aK and p
2aK of H2SO3 are 1.82 and 7.2 respectively. The pH after 20 mL of 0.16 M NaOH is added to
40 mL of 0.08 M H2SO3 is:
(a) 7.0 (b) 1.82 (c) 8.8 (d) 4.51
79. 18 ml of mixture of acetic acid and sodium acetate required 6 ml of 0.1 M NaOH for neutralization of
the acid and 12 ml of 0.1 MHCl for reaction with salt, separately. If pKa of the acid is 4.75, what is the
pH of the mixture?
(a) 5.05 (b) 4.75 (c) 4.5 (d) 4.6
80. What is the difference in pH for 1/3 and 2/3 stages of neutralization of 0.1 M CH3COOH with 0.1 M
NaOH.
(a) 2 log 3 (b) 2 log (1/4) (c) 2 log (2/3) (d) 2log 2
81. 100 mL of 0.02 M benzoic acid (pKa = 4.2) is titrated using 0.02 M NaOH. pH after 50 mL and 100
mL of NaOH have been added are
(a) 3.50, 7 (b) 4.2,7 (c) 4.2, 8.1 (d) 4.2, 8.25
82. In terms of K1, K2 and K3 of a weak triprotic acid H3B, the value of Kb for BH2
will be
(a) Kw/K1 (b) Kw/K2 (c) K2/Kw (d) Kw/K3
83. Blood is buffered with CO2 and HCO -
3 . What is the ratio of the base concentration to the acid (i.e.
CO2(aq. plus H2CO3)concentration to maintain the pH of blood at 7.4? The first dissociation constant of
H2CO3(H2CO3 ˆ ˆ ˆ†‡ ˆ ˆˆ H+ + HCO -
3 ) is 4.2 107
where the H2CO3 is assumed to include CO2(aq). i.e.,
dissolved CO2. (log 4.2 = 0.6232)
(a) 10.6 (b) 1.8 (c) 180 (d) 31
84. 0.1 M CH3COOH is diluted at 25oC (Ka = 1.8 10
5) then which of the following will be found correct
(a) [H+] will increase (b) pH will increase
(c) number of H+ will increase (d) all the above are correct
85. Which of the following statement are correct at 25oC.
(a) pKa for H3O+ is 15.74 (b) pKb for OH
is 1.74
(c) pKa + pKb = pKw for HCl & CIOH (d) degree of dissociation of water is .8 107
%
86. Which of the following pairs will not form a buffer solution?
(a) NaH2PO4 + Na3PO4 (b) NaH2PO4 + Na2HPO4
(c) Na2HPO4 + Na3PO4 (d) H3PO4 + Na3PO4
87. To solution of 20 ml of 0.1 M acetic acid, a solution of 0.1 M NaOH is added from burette. If „r‟ is the
ratio of [salt]
[acid], at what rate is the pH changing with respect to when 5 ml of the alkali have been added?
(a) 3 (b) 2.303
3 (c)
3
2.303 (d)
1
3 2.303´
88. A buffer solution is made by mixing a weak acid HA (Ka = 106
) with its salt NaA in equal amounts.
What should be the amount of acid or salt that should be added to make 90 ml of buffer solution in
which if 0.1 mole of strong acid are added into 1 L of this buffer solution then change in pH is unity?
(a) 10 mmoles (b) 22 mmoles (c) 9 mmoles (d) 11 mmoles
89. A solution is prepared by mixing 2 MHA (weak acid K = 1 106
) with 2 M HB (another weak acid
with K = 1 106
) in 1: 1 volume ratio. The pH of the resulting solution will be
(a) 6.010 (b) 2.849 (c) 6.3010 (d) 5.3010
90. The pH of 1.0 M NaHSO4 solution will be (given K1 and K2 for H2SO4 equal to and 102
respectively)
(a) nearly 1.0 (b) between 2 and 3 (c) between 1.2 and 1.8 (d) between 3 and 4
91. pH of a mixture of 1 M benzoic acid (pKa = 4.20) and 1 M C6H5COONa is 4.5, what is the volume of
benzoic acid required to prepare a 300 ml buffer [log 2 = 0.3]?
92. What is the oxidation number of sulfur in sulfurous acid?
(a) + 3 (b) + 4 (c) + 5 (d) + 6
93. Which of the following acid-base indicators is most suitable for the determination of the first end point
of the titration shown in Figure?
(a) Cresol red (Color change between pH = 0.2 and pH = 1.8)
(b) p-Xylenol blue (color change between pH = 1.2 and pH = 2.8)
(c) Bromocresol blue (color change between pH = 3.0 and pH = 4.6)
(d) Bromocresol green (color change between pH = 3.8 and pH = 5.4)
94. H2SO3 can act as a Lewis acid probably because sulfurous acid:
(a) is a proton donor (b) Accepts a pair of electrons from another species
(c) Reacts with NaOH which is a strong base (d) Possesses oxygen atoms
95. If no catalyst was used in Reaction – I, which of the following would experience a change in its partial
pressure when the same system reaches equilibrium in presence of a catalyst?
(a) There will be no change in the partial pressure of any of the reactants
(b) SO3(g) (c) SO2(g) (d) O2 (g)
96. If the temperature was decreased in Reaction – I, which of the following would experience an increase
in its partial pressure when the same system reaches equilibrium?
(a) There will be no change in the partial pressure of any of the reactants
(b) SO3(g) (c) SO2(g) (d) O2 (g) and SO2(g)
97. Reaction – I is usually carried out at atmospheric pressure. During the reaction, before equilibrium was
reached, the mole fractions of SO2(g) and SO3(g) were 1/2 and 1/6 respectively. What was the partial
pressure of O2(g)?
(a) 0.66 atm (b) 0.16 atm (c) 0.50 atm (d) 0.33 atm
98. What is the pH of 0.01 M H2SO3
(a) 1.0 (b) 2.0 (c) 3.0 (d) 4.0
99. At 300 K and 1.0 atm. pressure the density of gaseous HF is found to 3.1 g/L [Atomic mass H = 1, F =
19]. This means:
(a) HF gas consists of HF, H2 and F2 molecules
(b) HF gas consists of clusters of HF molecules such that each cluster consists of 4 HF molecules
bonded through H-bonds.
(c) A cluster consists of 6 HF molecules bonded with H-bonds
(d) A cluster consists of 2 HF molecules which are covalently bonded with each other
100. If the solubility of Ag2SO4 in 102
M Na2SO4 solution be 2 108
M then Ksp of Ag2SO4 will be
(a) 32 1024
(b) 16 1018
(c) 32 1018
(d) 16 1024
101. The solubility product for SrF2 is 7.9 1011
. A solution is 0.01 M in NaF. The minimum concentration
of SrCl2 in the solution required to start the precipitation of SrF2 is equal to:
(a) 0.89 105
M (b) 0.79 106
M (c) 0.79 108
M (d) 0.89 107
M
102. The number of millimoles present per liter of solution of CH3COONa so that 150 ppm (150 moles of it
gets hydrolysed out of one million moles added) of it is hydrolysed if Ka = 1.8 105
is
(a) 25 (b) 35 (c) 45 (d) 55
103. The CO in a 20.3 L sample of gas was converted to CO2 by passing the gas over iodine pentoxide
heated to 150oC: I2O5(s) + 5CO(g) 5CO2(g) + I2(g).
The iodine distilled at this temperature and was collected in an absorber containing 8.25 mL of 0.01101
M Na2S2O3. The excess hypo was back-titrated with 2.16 mL of 0.00947 M I2 solution. The milligrams
of CO in 1 L of the original gas sample was therefore
(a) 3.2 (b) 0.283 mg (c) 0.394 mg (d) 0.506 mg
104. What is the pH after addition of 40 mL of 0.1 M NaOH in the titration of 50 mL of 0.1 M anilinium
chloride?
(a) 3.2 (b) 4.2 (c) 5.2 (d) 6.2
105. If a titration curve (pH versus volume of NaOH) is constructed for the titration of question above, the
magnitude of its slope will be found to be maximum at
(a) 20 mL (b) 40 mL (c) 50 mL (d) 60 mL
106. A solution containing 0.1 mole/L HN3 and 0.2 mol/L NaN3 has a pH = 4.8. The Ka of HN3 is
(a) 2 104
(b) 4 102
(c) 5 103
(d) 3 105
107. The pH of a 0.01 M solution of erbium chloride ErCl3. 6H2O is 5.3. The ionization constant of
[Er(H2O)6]3+
is
(a) 1.5 109
(b) 2.5 109
(c) 1.5 106
(d) 2.5 106
Passage
Read the following passage and answer the question numbered 1 to 5. They have only one correct
option)
During a particular acid – base titration, the principal species either (i) HCl and H2X, (ii) H2X and
NaHX, (iii) NaHX and Na2X or (iv) Na2X and NaOH, where H2X is weak dibasic acid with Ka1 =
1.0 104 and ka2 = 1.00 108. It is known that the concentrations of the principal species are in the
range 0.01 – 0.5 M. The pH of a 0.1 M H2X solution is about 2.5, the pH of 0.1 M NaHX solution is
about 6 and the pH of 0.1 M Na2X solution abut 11. These pH corresponds to various equivalence
points.
108. If 50 ml of any of the above mixture required 14 ml of 0.25 M NaOH to reach anequivalence point at
pH 6.0 and an additional 33.00 ml to reach an equivalence pint at pH = 11, which pair of principal
special is present in mixture and what are the two concentrations?
(a) 0.08 M HCl + 0.06 M H2X (b) 0.06 M HCl + 0.08 M H2X
(c) 0.095 M H2X and 0.07 M NaHX (d) 0.07 M H2X and 0.095 M NaHX
109. 1f 50 ml of the mixture required 28 ml of 0.25 NaOH to reach an equivalence point at pH 6 and an
additional 12 ml to reach an equivalence point at pH 11. Which two principal species are present and
what are their concentrations?
(a) HCl (0.06 M) + H2X (0.08 M) (b) HCl(0.08 M) + H2X (0.06M)
(c) NaHX (0.12 M) + Na2X (0.04 M) (d) HCl (0.05 M) + NaHX (0.04 M)
110 If 50 ml of mixture required 8 ml of 0.25 M HCl to reach equivalence point at pH 6 and an additional
32 ml to reach an equivalence point at pH 2.5, which two principal species are present and what are
their concentrations?
(a) H2X(0.01 M) 0.04 M Na2X (b) 0.12 M NaHX + 0.04 M Na2X
(c) 0.04 M NaHX + 0.12 M Na2X (d) 0.05 M NaHX + 0.05 M Na2X
111. If 50 ml of mixture required 12 ml of 0.25 HCl to reach equivalence point at pH = 11 and an additional
9.00 ml to reach an equivalence point at pH = 6. Which two principal species are present and what are
their concentrations.
(a) 0.06 M NaOH + 0.045 M Na2X (b) 0.045 M NaOH + 0.06 M Na2X
(c) 0.06 M Na2X + 0.06 M NaHX (d) 0.06 M Na2X only
112. If 50 ml of the mixture required 11 ml of 0.25 M HCl to reach an equivalence point at pH 2.5 and a
separate 50 ml portion of the mixture required 28ml of 0.250 M NaOH to reach an equivalence point at
pH 6. What two principal species are present and what are their concentrations?
(a) 0.12 M NaHX + 0.05 M Na2X (b) 0.10 M NaOH and 0.12 M NaHX
(c) 0.055 M H2X and 0.14 M NaHX (d) 0.14 M H2X and 0.055 M NaHX
113. A weak acid HX titrated with 0.1 M NaOH. In which titration will the change in pH at the equivalence
point be greatest?
(a) 3 m moles of HX in 80 mL of water (b) 3 mmoles of HX in 125 mL of water
(c) 4 mmoles of HX in 80 mL of water (d) 4 mmoles of HX in 100 mL of water
114. To 50 mL of 0.1 M H3PO4 is added 50 mL of 0.2 M NaOH. The pH of the resulting solution would be
in the range.
(a) 4 to 5 (b) 6 to 7 (c) 9 to 10 (d) 13 to 14
115. For the acid H2X, pK1 = 4 and pK2 = 10. Which of the following indicators (with their ranges provided)
is most suitable for the titration H2X + OH HX
+ H2O?
(a) Menthyl orange (3.1 to 4.4) (b) Bromocresol green (3.8 to 5.4)
(c) p-nitrophenol (5.6 to 7.6) (d) Phenolphthalein ( 8 to 9.6)
116. The concentration of free HN3 in a 0.01 M solution of KN3 if Ka = 1.9 105
is
(a) 2.3 mol/ML (b) 3.3 mol/ML (c) 4.3 mol/ML (d) 5.3 mol/ML
117. To the solution of a weak monobasic acid whose pH was 3 some amount of an HCl solution is added.
This could result into
(a) an increases in pH only (b) a decrease in pH only
(c) either increase or decrease in pH (d) no change in pH only
118. The pH of a solution of NaHSO4 (Ka = 1.26 102
) will
(a) be > 7 (b) be < 7 (c) depend on its concentration (d) be independent of dilution
119. The volume of 0.1 M Na2SO4 needed to be added to 10 mL of 0.1 M HCl to change the pH from 1.00
to 1.50 is:
(a) 6.6 mL (b) 4.4 mL (c) 2.2 mL (d) 1.1 mL
120. 0.5 L of 0.5 M CH3COOH and 0.5 L of 0.25 M CH3COONa are available. What maximum volume of a
buffer with a pH = 4.58 can be prepared using only these two resources?
(a) 0.86 L (b) 0.66 L (c) 0.46 L (d) 0.96 L
121. Which of the following solution will exhibit the least change in pH on dilution to double their volumes?
(a) HCl solution (b) CH3COOK-CH3COOH solution
(c) CH3COONNa solution (d) NH4OH solution
122. Given Hn = 13600 cal/eq, the final temperature reached if 20 mL of 0.1 M NaOH at 20oC is mixed
with 40 mL of 0.6 M HCl at 30oC assuming adiabatic mixing is (C = o
1 cal
C - mLfor solution)
(a) 28.12 oC (b) 26.66
oC (c) 27.12
oC (d) 25
oC
123. Both conc. Being 1 M, the factor by which the percent hydrolysis of CH3COO is greater in
CH3COONH4 than in CH3COONa is
(a) 236 (b) 136 (c) 36 (d) 3
124. When a drop of a concentrated HCl solution is added to one litre of pure water at 25oC the pH drops
from 7 to about 4. When the second drop of the same HCl solution is added the pH further drops to
about:
(a) 3.7 (b) 2 (c) 1 (d) 3.4
125. A 0.01 Molar solution of hydrazinium iodide is found to be exactly 1 percent hydrolysed. The Kb of
hydrazine is.
(a) 105
(b) 106
(c) 107
(d) 108
126. What are concentration of Ag+ and Ag(NH3)2+ in a solution prepared by adding 0.10 mole of AgNO2 to
1.0 L of 3.0 M NH3? Kf[Ag(NH3)2]+ = 1.6 10
7
127. Calculate following if Ksp of Zn(OH)2 is 4.1 1017
(a) Calculate the pH of saturated solution of Zn(OH)2
(b) Calculate the molar solubility of Zn(OH)2 in a 0.1 M NaOH if Kf for Zn(OH) 2
4
- is 3 1015
.
128. Which of the following options is incorrect:
(a) pH at half equivalence point of a weak acid (HA) equal to pKb of its conjugate base
(b) An aqueous solution of sodium acetate will be basic due to anionic hydrolysis
(c) pKa for H3O+ at 298 K is 1.74
(d) On dilution of a solution of a weak acid, degree of ionization will increase but [H+] will decrease
129. The solubility product values of barium sulphate and barium carbonate are 1.0 1010
and 5.0 109
respectively. When these two salts are equilibirated in pure water then ratio of 2-
4SOé ùë û/
2-
3COé ùë ûis.
(a) 0.02 (b) 0.10 (c) 0.05 (d) 0.12
130. The pH of a solution containing 0.1 M CH3COONa and 0.1 M (C2H5COO)2 Ba will be Ka (CH3COOH)
= 2 105
, Ka(C2H5COOH) = 1.5 105
(a) 8.13 (b) 9.13 (c) 10.18 (d) 11.18
131. An equimolar solution of CH3COOH and C2H5COONa will be (Take Ka‟s from above question)
(a) acidic (b) neutral (c) alkaline (d) insufficient data to predict
132. The pKa of iodic acid HIO3 is log 6. Calculate the pH of a 1 M HIO3 solution
(a) 1og 6 (b) log 5 (c) log 4 (d) log 3
133. Calculate the pH of a solution of CaCO3 having [Ca+2
] = 1.3 104
M, [CO 2
3
- ] = 3.8 105
M and
[HCO 3
- ] = 8.8 105
M. Calculate the K2 of carbonic acid using this information.
134. Calculate the volume (mL) of 0.1 M Na2SO4 which must be added to 10 mL of HCl (pH = 1.0) so that
pH of the resulting solution becomes two. (Ginen K2 for H2SO4 = 102
]
135. 25 mL of a sample of clear saturated solution of PbI2 requires 10 mL of a certain AgNO3 (aq) for its
titration. What is the molarity of this AgNO3(aq)? Ksp for PbI2 = 4 109
.
136. A solution contains a mixture of Ag+ (0.10 M) and Hg 2
2
+ (0.10 M) which are to be separated by
selective precipitation. Calculate the maximum concentration of iodide ion at which one of them gets
precipitated almost completely. What % of that metal ion is precipitated? KSP of AgI = 8.5 1017
and
KSP of Hg2I2 = 2.5 1026
.
137. Freshly precipitated Al and Mg hydroxides are stirred vigorously in a buffer solution containing 0.25 M
of NH4 Cl and 0.05 M of NH4OH. Calculate [Al3+
] and [Mg2+
] in solution Kb for NH4OH = 1.8 105
.
KSP of Al(OH)3 = 6 1032 and KSP of Mg(OH)2 = 8.9 1012
138. A particular saturated solution of silver chromate, Ag2CrO4, has [Ag+] = 5 10
5 and [CrO 2
4
- = 4.4
104
M. What is value of KSP for Ag2CrO4?
139. KSP of Al(OH)3 is 1.0 1015
M. At what pH does 1.0 103
MAl3+
precipitate on the addition of buffer
of NH4Cl and NH4OH solution?
140. 10.0 mL of a weak acid HA, 1.0 M (Ka = 105
)is taken in a beaker and to this 1.0 M NaOH solution is
gradually added. Calculate the [H+] for the solution in the beaker at the following additions of NaOH.
(a) 0.1 mL NaOH (b) 1.0 mL NaOH (c) 5.0 mL NaOH (d) 10.0 mL NaOH
141. Two buffer solutions (X) and (Y) of pH = 4.0 and 6.0 respectively are prepared from weak acid HA (Ka
= 105
) and salt NaA. Both the buffers are 0.50 M in HA. Calculate the [H+] for the solution obtained
by mixing equal volumes of (X) & (Y).
142. How many mL of 0.001 M HCl should be added to 10 mL of 0.001 N NaOH to change its pH by one
unit.
143. Will a precipitate form when 0.150 L of 0.10 M Pb(NO3)2 and 0.100 L of 0.20 M NaCl are mixed? KSP
(PbCl2) = 1.2 105
144. Calculate the molar solubility of Fe(OH)3 in a buffer solution that 0.10 M in NH4Cl and 0.10 M in NH3.
Kb(NH3) = 1.8 105
KSP[Fe(OH)3] = 2.6 1039
145. What compound, if any, will precipitate when 80 mL of 1.0 105
M Ba(OH)2 is added to 20 mL of 1.0
105
M Fe2(SO4)3.
146. Saturated CaC2O4(aq) is prepared and 250.0 mL of the solution is withdrawn and titrated with 6.3 mL
of 0.00102 M KMnO4(aq). What is the value of KSP for CaC2O4? The titration reaction is
5C2O2
4
- (aq) + 2MnO 4
- (aq) + 16 H+ (aq) ¾ ¾® 2Mn
2+ (aq) + 8H2O + 10CO2(g)
147. An aqueous solution of a metal bromide MBr2(0.05 M) is saturated with H2S. What is the minimum pH
at which MS will precipitate?
KSP(MS) = 6.0 1021
Concentration of saturated H2S = 0.1 M
K1 (H2S) = 1 107
, K2(H2S) = 1.3 1013
Answer Key
1. 2. (a) 3. (a) to the left (b) to the right
4. 5. 6. 7. Ka = 1.54 1010
8. Kb = 1.8 105
9. [OH] = 0.5 10
8 M 10.
11. 0.84 atm
12. (a) 0.15 N acidic (b) 0.133 N acidic (c) neutral (d) neutral (e) 0.05 N basic
(f) neutral (g) 0.05 N basic
13. Ka [CN] = 2.04 10
5 14. (a) [OH
] = [NaOH] = 10
4 (b) [OH
] = 0.5 10
2 M
15. (a) 1.699 (b) 2 (c) 12.3010 (d) 12
16. (a) 8.204 (b) 5.22 (c) 6.37 (d) 0 (e) 13.3
17. (a, d) 18. Kb = 1.8 105
19. (i) [H3O+] = 6 10
4 M (ii) 3 % ionized at 0.02 M (iii) 3.22
20. 16 atm 21. 9.0 22. [XO2] = 0.0141 M
23. (b) 24. Ka(II) = 1.8 105
25.
26. 27. 28. (c) 29. (b)
30. 0.40 atm1
31. 38.2 % 32. (d) 33. (c)
34. 35. (a) 36. (a) 37. (b)
38. 900 mL 39. 2
AP = 0.5 atm, PC = 0.4 atm
2A
PC
= 0.3 atm
40. 0.5 41. 2.37, V = 2.7 104 litres 42. 3.7 10
4
43. (a,c,d) 44. pH = 6.66 45. [H+] = 7.071 10
3
46. 4.47 percent 47. 20.9 %
48. (a) pOH will increase so pH decrease (b) [H+]will decrease so pH increase
(c) No change (remains same)
49. [S2
] = 2.5 1015
50. pH = 1.0 51. C1 = 6.66 M
52. (d) 53. (c, d) 54. (c) 55. (b)
56. (c) 57. 1.66 % 58. (b) 59. (d)
60. (d) 61. (c) 62. (d) 63. (b)
64. (d) 65. (c) 66. (b) 67. (b)
68. (a) Kc = 1
12 litre
2 mol
2 (b) 4M, 1.5 M 69. (d)
70. (b) 71. (c) 72. (a) 73. (d)
74. (d) 75. 76. pH 6.39 77. (a)
78. (d) 79. 5.05 80 (d) 81. (c)
82. (b) 83. (a) 84. (b, c) 85. (b,d)
86. (a, d) 87. (c) 88. (d) 89. (b)
90. (a) 91. 92. (b) 93. (c)
94. (b) 95. (a) 96. (b) 97. (d)
98. (b) 99. (b) 100. (b) 101. (b)
102. (a) 103. (a) 104 (c) 105. (c)
106. (d) 107. (b) 108. (d) 109. (b)
110. (b) 111. (a) 112. (d) 113. (c)
114. (c) 115. (c) 116. (a) 117. (c)
118. (c) 119. (a) 120. (a) 121. (b)
122. (c) 123. (a) 124. (a) 125. (d)
126. 7.97 1010
, 0.1 M 127. 128. (a)
129. 130. (b) 131. (a) 132. (d)
133. 9.944, 4.84 1011
134. 135. 5 103
136.
137. 1.28 1015
M, 0.686 M 138. 139. 140.
141. 142. 143. 144. 145. Fe(OH)3
146. 147.