# REDOX REACTIONS AND ELECTROCHEMISTRY – 3

**1)** The pH of N/100 H_{2}SO_{4} solution is

**a)** 1

**b)** 2

**c)** 3

**d)** 4

**2) **The pH of N/10 NaOH is

**a)** 11

**b)** 13

**c)** 10

**d)** 8

**3)** @ The pH of 0.5 M KOH is

**a)** 13.699

**b)** 11.0

**c)** 11.699

**d)** 12.699

**4)** The pH of a solution of HCl is 4. The molarity of the solution is

**a)** 4.0

**b)** 0.4

**c)** 0.0001

**d)** 0.04

**5)** @ 0.1 N solution of a weak base has a pH = 9. What is the percentage ionisation of the base ?

**a)** 01.%

**b)** 0.01%

**c)** 0.2%

**d)** 0.02%

**6)** The pH of a solution is 4. The H^{+} ion concentration of the solution is

**a)** moles/litre

**b)** 4 moles/litre

**c)** moles/litre

**d)** 0.4 moles/litre

**7)** @ The pH of a solution at 25Â°C is 2. If the pH is to be doubled then the hydronium ion concentration of the solution should be

**a)** Halved

**b)** Doubled

**c)** Increased by 100 times

**d)** Decreased by 100 times

**8) **A solution of pH 9 is one thousand times as basic as a solution of pH… ?

**a)** 6

**b)** 7

**c)** 8

**d)** 10

**9) **The pH of a solution is 4. What should be the change in H^{+} ion concentration of the solution if the pH is to be increased to 5?

**a)** Halved

**b)** Doubled

**c)** Decreased by 10 times

**d)** Decreased to half of its original value

**10)** If 900 ml of more distilled water is

added to 100 ml of aqueous HCl of pH = 1.0, the pH of the resulting solution will become

**a)** 1.0

**b)** 2.0

**c)** 4.0

**d)** 7.0

**11) **At 80Â°C, the H_{3}O^{+} ion concentration in pure water is 10^{-6}. What is the value of the ionic product at 80Â°C in moles^{2}litre^{-2} ?

**a)**

**b)**

**c)**

**d)**

**12)** If the [OH^{–}] ion concentration is 1 x 10^{-8} ion/litre, its pH is

**a)** 6

**b)** 7

**c)** 5

**d)** 8

**13)** The value of dissociation constants of some acids are given below. Indicate which is the strongest acid in water .

**a)**

**b)**

**c)**

**d)**

**14)** The value of pKw at 25Â°C is

**a)** + 7

**b)** – 14

**c)** + 14

**d)**

**15) **Which of the following when added to 35 ml of 0.1 M KOH, would cause the largest change in pH ?

**a)** 2.5 ml of 1.0 M HCl

**b)** 25 ml of 0.2 M HCl

**c)** 25 ml of 0.05 M HCl

**d)** 25 ml of distilled water

**16)** The pH of boiling water (373 K) is : Given Kw=10^{-12} (at 373 K)

**a)** 12

**b)** 8

**c)** 6

**d)** 2

**17)** At 90Â°C pure water has [H_{3}O^{+}] = 10^{-6} mole litre^{-1}. What is the value of Kw at 90Â°C ?

**a)**

**b)**

**c)**

**d)**

**18)** @ The ionisation constant of water at 37Â°C is 2.42 x 10^{-14 }mole^{2 }litre^{-2}. What is the pH for a neutral solution at this temperature?

**a)** 0

**b)** 7.2

**c)** 7.0

**d)** 6.82

**19)** What is the pH of a neutral solution at 50Â°C. ( pKw = 13.2 at 50Â°C ?)

**a)** 6.0

**b)** 6.63

**c)** 7.13

**d)** 7.0

**20)** The pH of a solution is 5.0. To this solution sufficient acid is added to decrease the pH to 2.0. The increase in concentration of H^{+} ions is

**a)** 1000 times

**b)** 5/2 times

**c)** 100 times

**d)** 5 times

**21)** 0.4 g of NaOH present in one litre solution shows the pH

**a)** 12

**b)** 2

**c)** 6

**d)** 10

**22)** @

A certain buffer solution contains equal concentrations of X^{–} and HX. The K_{b} for X^{–} is 10^{-10}. The pH of the buffer is

**a)** 4

**b)** 7

**c)** 14

**d)** 10

**23) **The pH of a 10^{-10} M HCl solution is approximately

**a)** 10

**b)** 7

**c)** 1

**d)** 14

**24)** 10^{-6} M HCl is diluted to 100 times. Its pH is

**a)** 6.0

**b)** 8.0

**c)** 6.95

**d)** 9.5

**25)** @ The pH of 10^{-10} M NaOH solution is nearest to

**a)** 10

**b)** 7

**c)** 4

**d)** –10

**26)** 10^{-6} M NaOH is diluted 100 times. The pH of the diluted base is

**a)** Between 6 and 7

**b)** Between 10 and 11

**c)** Between 7 and 8

**d)** Between 5 and 6

**27)** The pH of a 10 M solution of HCl is

**a)** Less than zero

**b)** Zero

**c)** 2

**d)** 1

**28)** Which buffer solution will have a pH>7 ?

**a)**

**b)** HCOOH+HCOONa

**c)**

**d)**

**29)** Any buffer can be used as a buffer upto

**a)** 10 pH units

**b)** 5 pH units

**c)** 2 pH units

**d)** 1 pH unit

**30)** The pH of 10^{-8} M NaOH is

**a)** 8.0

**b)** 6.96

**c)** 12.0

**d)** 7.04

**31)** The pH of a solution is 5.96. If H^{+} ion concentration decreases by 100 times, then the nature of the solution is

**a)** Acidic

**b)** Basic

**c)** Neutral

**d)** Amphoteric

**32)** The pH value of a 10^{-5} M aqueous solution of NaOH is

**a)** 5

**b)** 7

**c)** 9

**d)** 11

**33)** The pH of H_{2}SO_{4} = 2. Its molar concentration is

**a)** 0.01

**b)** 0.005

**c)** 0.02

**d)** 0.05

**34)** The pH of a 0.005 M aqueous solution of sulphuric acid is

**a)** 0.005

**b)** 2

**c)** 1

**d)** 0.01

**35)** Assuming complete dissociation, the pH of a 0.01 N NaOH solution is

**a)** 2.0

**b)** 14.0

**c)** 12.0

**d)** 0.01

**36)** @ The pH of a solution is 4.0 at 25Â°C. Its pOH would be (Kw=10^{-14}).

**a)** 4.0

**b)** 10.0

**c)** 8.0

**d)** 6.0

**37)** 50 ml of 2N CH_{3}COOH mixed with 10 ml of IN sodium acetate solution will have an approx. pH of (K_{a}= 10^{-5})

**a)** 4

**b)** 5

**c)** 6

**d)** 7

**38)** When 1.0 ml of dilute HCl is added to 100 ml of a buffer solution of pH = 4, the pH of the solution becomes

**a)** 7

**b)** 2

**c)** 10

**d)** Does not change

**39)** If the H^{+} ion concentration of a given solution is 5.5 x 10^{-3} M, the pH of the solution is

**a)** 2.26

**b)** 3.40

**c)** 3.75

**d)** 47.6

**40)** The pH of a solution containing 10 ml of 0.1 N NaOH and 10 ml of 0.05 N H_{2}SO_{4 }would be

**a)** 0

**b)** 1

**c)** 7

**d)** > 7

**41)** How many times more acidic is a solution of pH = 2 than a solution of pH = 6 ?

**a)** 10000

**b)** 12

**c)** 400

**d)** 4

**42)** A 0.2 M solution of HCOOH is 3.2% ionised. Its ionisation constant is

**a)**

**b)**

**c)**

**d)**

**43)** An aqueous solution of 0.1 M NH_{4}Cl will have a pH close to

**a)** 9.1

**b)** 8.1

**c)** 7.1

**d)** 5.1

**44)** @ Which solution will have a pH closest to 1.0 ?

**a)** 100 ml of M/10 HCl + 100 ml of M/10 NaOH

**b)** 55 ml of M/10 HCl + 45 ml of M/10 NaOH

**c)** 10 ml of M/10 HCl + 90 ml of M/10 NaOH

**d)** 75 ml of M/5 HCl + 25 ml of M/5 NaOH

**45)** The H^{+} ion concentration in 0.001 M CH_{3}COOH (K_{a}= 1.8x 10^{-5}) is 1.34x 10^{–} ^{4}g

ion/litre. The H^{+} ion concentration if 0.164 g. of CH_{3}COONa is added to a litre of 0.001 M CH_{3}COOH will be

**a)**

**b)**

**c)**

**d)**

**46)** The [H_{3}O^{+}] in rain water of pH 4.35 is

**a)**

**b)**

**c)**

**d)**

**47)** The pH of 0.1 M HCl is approx. 1.0. The approximate pH of 0.05 M H_{2}SO_{4} is

**a)** 0.05

**b)** 0.5

**c)** 1

**d)** 2

**48)** K_{a} for HCN is 5 x 10^{-10} at 25Â°C. To maintain a constant pH = 9, the volume of 5M KCN solution required to be added to 10 ml of 2M HCN solution is

**a)** 4 mL

**b)** 7.95 mL

**c)** 2 mL

**d)** 9.3 mL

**49)** A 0.01 M ammonia solution is 5% ionised. The concentration of OH^{–} ions is

**a)** 0.005 M

**b)** 0.0001 M

**c)** 0.0005 M

**d)** 0.05 M

**50)** The pH of a 0.02 M HCl solution is

**a)** 2

**b)** 1.7

**c)** 0.3

**d)** 2.2

**51)** The pH of a 0.01 M solution of CH_{3}COOH having 12.5% degree of dissociation is

**a)** 4.509

**b)** 3.723

**c)** 2.903

**d)** 5.623

**52)** The possible H^{+} ion concentration for an acidic solution is

**a)**

**b)**

**c)**

**d)**

**53)** @ The pH of the solution produced when an aqueous solution of strong acid of pH = 5 is mixed with an equal volume of an aqueous solution of strong acid of pH = 3 is

**a)** 3.3

**b)** 3.5

**c)** 4.5

**d)** 4.0

**54)** The pK_{a} of an acid whose ionisation constant is 1 x 10^{-3} is

**a)** 3

**b)** – 3

**c)** -9

**d)** + 9

**55)** A buffer mixture of CH_{3}COOH and CH_{3}COOK has pH = 5.24. The ratio of

CH_{3}COO^{– }/CH_{3}COOH in this buffer is (pK_{a} =4.74).

**a)** 3 : 1

**b)** 1 : 3

**c)** 1 : 1

**d)** 1 :2

**56)** The weight of HCl present in one litre of solution, if the pH of the solution is 1, is

**a)** 3.65 g

**b)** 36.5 g

**c)** 0.365 g

**d)** 0.0365 g

**57)**

The pH of a solution formed by mixing 40 ml of 0.10 M HC1 and 10 ml of 0.45 M NaOH is.

**a)** 5

**b)** 8

**c)** 12

**d)** 10

**58)** 20 ml of 0.1 NHC1 is mixed with 20 ml of a 0.1 N KOH solution. The pH of the solution would be

**a)** 0

**b)** 7

**c)** 2

**d)** 9

**59)** The number of moles of [OH^{–}] ion in 0.3 litre of 0.0005 molar solution of Ba(OH)_{2} is

**a)** 0.0075

**b)** 0.0015

**c)** 0.0030

**d)** 0.0050

**60)** The pH of 0.05 M Mg(OH)_{2} is

**a)** 13

**b)** 10

**c)** 1

**d)** 0

**61)** pH of M/200 Ba(OH)_{2} solution (assuming complete dissociation) is

**a)** 2

**b)** 12

**c)** 12.70

**d)** 11.6

**62)** 0.04 g of pure NaOH is dissolved in 10 litres of distilled water. The pH of the solution is

**a)** 9

**b)** 10

**c)** 11

**d)** 12

**63)** The dissociation constant of an acid HA is 1 x 10^{-5}. The pH of a 0.1 M solution of the acid HA will be approximately

**a)** 3

**b)** 5

**c)** 1

**d)** 6

**64)** 10 ml of a solution contains 0.1 M NH_{4}C1 + 0.1 M NH_{4}OH. What addition would not change the pH of the solution ?

**a)** Adding 1 ml water

**b)**

**c)**

**d)**

**65)** When 10^{-8} mole of HCl is dissolved in one litre of water, the pH of the solution is

**a)** 8

**b)** 7

**c)** Above 8

**d)** Below 7

**66)** An aqueous solution contains a substance which yields 4×10^{-3} mole litre^{-1} ion of H_{3}O^{+}. If log 2 = 0.3010, the pH of the solution is

**a)** 1.5

**b)** 2.398

**c)** 3.0

**d)** 3.4

**67)** The pH of 1% ionised 0.1 M solution of acetic acid is

**a)** 1

**b)** 2

**c)** 3

**d)** 11

**68)** A monoprotic acid is 1.00 M solution and is 0.001% ionised. The dissociation constant of the acid is

**a)**

**b)**

**c)**

**d)**

**69)** The pH of a 1 x 10^{-8} M aqueous solution of HCl is slightly less than 7 because

**a)** The ionisation of HCl is incomplete

**b)** The ionisation of water negligible

**c)** The ionisation of water at such a low concentration of HCl is significant

**d)**

**70)** @ One mole of water contains 10^{-7} moles of H^{+} ions. The degree of ionisation of water is

**a)**

**b)**

**c)**

**d)**

**71)** @ The pH of a solution whose [H^{+}] is one mole per litre is

**a)** 1.0

**b)** 0.1

**c)** 0

**d)** 1.5

**72)** HClO is a weak acid. The [H^{+}] in 0.1 M solution of HClO (K_{a} = 5x 10^{-8}) will be equal to

**a)**

**b)**

**c)**

**d)**

**73) **Which of the following will occur if a 0.1 M solution of a weak acid is diluted to 0.01 M at constant temperature ?

**a)**

**b)** The pH will decrease

**c)** The percentage of ionisation increases

**d)** The activation constant will increase

**74)** Which would decrease the pH of 25 cm^{3} of a 0.01 M HCl solution?

**a)** The addition of Mg

**b)**

**c)**

**d)** None

**75)** @ The pH of 1 M CH_{3}COONa solution is: (K_{a}=1.810^{-5}, K_{w} = 10^{-14} mole^{2} litre^{2-})

**a)** 2.4

**b)** 3.6

**c)** 4.8

**d)** 9.4

**76)** @

How many H^{+} ions are contained in 1 ml of a solution whose pH = 13 ?

**a)**

**b)**

**c)**

**d)**

**77)** What is the value of [H^{+}][OH^{–}] in a 1 M solution of NaOH?

**a)**

**b)**

**c)** 10

**d)**

**78)** A solution is prepared by mixing 500 ml of 0.2 M CH_{3}COOH and 500 mL of 0.4 M CH_{3}COONa. What is the H^{+} ion concentration of the solution, if K_{a} for CH_{3}COOH is 1.8×10^{-5} ?

**a)**

**b)**

**c)**

**d)**

**79)** What is the pH of 10^{-3} M ammonium cyanide solution, if K_{HCN} = 7.2 x 10^{-11} and K_{NH3} = l.8×10^{-5} ?

**a)** 14

**b)** 9.7

**c)** 12.0

**d)** 7.5

**80)** 20 ml of HCl is completely neutralised with 40 mL of 0.05 M NaOH. The pH of the original HCl solution is

**a)** 3

**b)** 2

**c)** 1

**d)** 1.5

**81)** The concentration of acetic acid required to give 3.5 x 10^{-4} moles/litre of H^{+} ions is : (Given K_{a}= 1.8 x 10^{-5})

**a)**

**b)** 6.8

**c)** 1.94

**d)** 19.4

**82)** @ 100 ml of 0.1 M H_{2}SO_{4} is diluted to 250 ml. What is the increase in pH ?

**a)** 0.3979

**b)** 0.6990

**c)** 1.0969

**d)** None

**83)** Calculate the pH of a solution obtained by mixing 50 ml of N HCl and 30 ml of N NaOH.

**a)** 0.6021

**b)** 0.2106

**c)** 0.2602

**d)** None

**84)** The pH of a solution containing 40 g of NaOH in 500 ml water is

**a)**

**b)** 13.3010

**c)** 12

**d)** 12.3010

**85)** What is the ratio of [Salt]/[Acid] for a buffer solution of pH = 4.70, given that Ka=1.75 x 10^{-5} ?

**a)** 0.8772

**b)** 0.7872

**c)** 0.2778

**d)** None

**86)** @ What is the pH of a buffer solution containing 0.015M NH_{4}OH and 0.025M NH_{4}Cl? The K_{b }of NH_{4}OH = 1.5 x 10^{-5} and K_{w}= 1 x 10^{-14} .

**a)** 9.0335

**b)** 8.5

**c)** 7.0

**d)** 12.0

**87)** What is the pH of a buffer solution containing 12 g CH_{3}COOH and 16.4 g. of CH_{3}COONa in 500 ml of solution. K_{a} for CH_{3}COOH =1.8 x 10^{-5} ?

**a)** 4.7447

**b)** 4.4774

**c)** 4.4477

**d)** None

**88)** @ The pH of 0.4833 % solution of HCl is

**a)** 0.8239

**b)** 0.2389

**c)** 0.9328

**d)** None

**89)** What is the amount of acetic acid that must be dissolved in 100 mL of solution to get a pH = 2.4? The K_{a} for CH_{3}COOH = 1.85 x 10^{-5} and the mol. wt of CH_{3}COOH = 60 ?

**a)**

**b)**

**c)**

**d)**

**90)** What is the pH of 0.001 M solution of Ba(OH)_{2} assuming complete ionisation ?

**a)** 11.3

**b)** 12.4

**c)** 13.1

**d)** 10.5

**91)** A solution of HCl has a pH = 5. If one ml of it is diluted to one litre, what will be the pH of the resulting solution ?

**a)** 6.9788

**b)** 7.0

**c)** 7.9788

**d)** None

**92)** What volume of 0.1 M sodium formate solution should be added to 50 ml of 0.05 M formic acid to produce a buffer solution of pH = 4. Given pK_{a} = 3.80 ?

**a)** 39.62 ml

**b)** 62.39 ml

**c)** 93.26 ml

**d)** None

**93)** To prepare a buffer solution of pH = 6, by mixing CH_{3}COONa and CH_{3}COOH, the ratio of the concentration of salt and acid should be (Ka=10^{-5}).

**a)** 1:10

**b)** 10:1

**c)** 100 : 1

**d)** 1 : 100

**94)** The pH of a mixture of CH_{3}COOH + CH_{3}COONa after adding water shows a …… … value

**a)** Decreased

**b)** Increased

**c)** Constant

**d)** None

**95)** The pH of a 0.4 M HNO_{3} solution is

**a)** 2

**b)** 3

**c)** 0.398

**d)** 4

**96)** At 25 Â°C, the dissociation constants of CH_{3}COOH and the weak base BOH in aqueous solution are almost the same. The pH of a solution of 0.01 N CH_{3}COOH is 4.0 at 25Â°C. The pH of 0.1 N BOH solution at the same temperature would be

**a)** 4

**b)** 3

**c)** 10

**d)** 12

**97)** The concentration of [H^{+}] and the concentration of [OH^{–}] of a 0.1M aqueous solution of a 2% ionised weak acid is

**a)**

**b)**

**c)**

**d)**

**98)** The pH value of HCl and NaOH solution each of N/100 strength will be respectively

**a)** 2 and 2

**b)** 2 and 12

**c)** 12 and 2

**d)** 2 and 10

**99)** @ 50 ml of water is added to 50 ml solution of Ba(OH)_{2} of strength 0.01M. The pH value of the resulting solution will be

**a)** 8

**b)** 10

**c)** 12

**d)** 6

**100)** @ The dissociation constant of a weak monobasic acid K_{a} = 1 x 10^{-5}. The pH of 0.1M solution of that acid would be

**a)** 5

**b)** 1

**c)** 2

**d)** 3

Answer :