Objective Type (More than One Choice Correct)

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1. for the following balanced redox reaction,

2MnO^4¯ + 8H⁺ + Br² ↽⇀ 2Mn⁺² + 2 BrO^3¯ + 2H²O If the molecular wt. of MnO4¯, Br2 be Mx, My respectively, then

(a) equivalent wt. of MnO^4¯ is Mx/5 (b) equivalent wt. of Br² is My/10 (c) the n-factor ratio of Mn⁺² to BrO3¯ is 1 : 1 (d) none of these

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2. When a mixture of Cu²S and CuS is titrated with Al(MnO⁴) in acidic medium, then the oxidation product of Cu²S and CuS are Cu⁺², and Al(MnO⁴)³ be M, M′ and M″ respectively, then which of the following statement are correct?

(a) Equivalent weight of Cu²S is M

8 (b) Equivalent weight of CuS is M′/5

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3. For the balanced redox reaction a NO3¯ + b As2S3 + 4 H2O → x AsO4– 3 + y NO + z 3 SO4–2 + 8H which of the following statements are correct?

(a) equivalent wt. of As²S³ is M/28 where M is molecular wt. of As²S³ (b) The value of a : b = 28 : 3

x y is 1 (d) The value of z x−

3 is 1

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4. When non-stoichiometric compound Fe^0.95O is heated in presence of oxygen, then it converts into Fe²O³, then which of the following statements are correct?

(a) Equivalent weight of Fe0.95O is M

0.85 where M is molecular weight of Fe0.95O (b) The number of moles of Fe⁺³ and Fe⁺² 1 moles Fe^0.95O and 0.1 and 0.85 respectively (c) The number of moles of Fe⁺³ and Fe⁺² in 1 mole of Fe^0.95O are 0.85 and 0.10 respectively

(d) The % composition of Fe⁺² and Fe⁺³ in the non stoichiometric compound is 89.47% and 10.53%

respectively

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5. When FeS² is oxidized with sufficient O², then its oxidation product is found to be Fe²O³ and SO², if the molecular weight of FeS², Fe²O³ and SO² are M, M′ and M″, then which of the following statements are correct?

(a) Equivalent wt. of FeS2 is M/11 (b) The molar ratio of FeS2 to O2 is 4 : 11 (c) The molar ratio of FeS² to O² is 11 : 4 (d) The molar ratio of Fe²O³ and SO² is 1 : 4

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6. 40 g NaOH, 106 g Na2CO3 and 84 g NaHCO3 is dissolved in water and the solution is made 1 litre. 20 mL of this stock solution is titrated with 1N HCl, hence which of the following statements are correct?

(a) the titre reading of HCl will be 40 mL, if phenolphthalein is used indicator from the very beginning

(b) the titre reading of HCl will be 60 mL if phenolphthalein is used indicator from the very beginning.

(d) the titre reading of HCl will be 880 mL, if methyl orange is used as indicator from the very beginning

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7. 150 mL M

10 Ba(MnO⁴)² in acidic can oxidize completely

(a) 150 mL 1M Fe⁺² (b) 50 mL 1M FeCrO⁴

(a) Molarity (b) Normality (c) Molality (d) Mole fraction

behaves as reducing agent, then its equivalent weighted are

equal to half of its molecular weight respectively?

(b) 1000 mL of 1 N solution of each is neutralized by 1000 mL of 1 N Ca(OH)²

Then which of the following statements are correct?

(a) the equivalent weight of H³PO⁴ is 49

(b) the resulting solution is neutralized by 1 mole of KOH

11. The density of 3M sodium thiosulphate is 1.25 g mL^–1. Identify the correct statements among the following

(a) % by the weight of sodium thiosulphate is 37.92 (b) The mole fraction of sodium thiosulphate is 0.065 (c) The molality of Na⁺ is 2.53 and S₂O₃^2– is 1.25 (d) All of these

12. A 5 L vessel contains 2.8 g of N₂. When heated to 1800 K, 30% molecules are dissociated into atoms (a) Total number of moles in the container will be 0.13

(b) Total number of molecules in the container will be close to 0.421 × 10²³ (c) Total number of moles in the container will be 0.098

(d) All of these

13. The density of air is 0.001293 g/cm³ at STP. Identify which of the following statement is correct (a) Vapour density is 14.48

(b) Molecular weight is 28.96

(d) Vapour density and molecular weight cannot be determined

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14. Cr2O72– is reduced to Cr³⁺ by Fe²⁺. Identify the incorrect statement from the following (a) 6 moles of Fe²⁺ are oxidised to Fe³⁺ ions (b) The solution becomes green (c) The solution becomes yellow (d) 3 moles of Fe²⁺ get oxidised to Fe³⁺

15. Which of the following has same mass

(a) 1.0 mole of O₂ (b) 3 × 10²³ molecules of SO₂

16. A solution of KMnO₄ to be used in acidic medium is prepared by dissolving 1.58 g L^–1. The solution is

(a) M/100 (b) N/20 (c) M/50 (d) N/50

17. The mole fraction of NaCl in aqueous solution is 0.2. The solution is

(a) 13.9 m (b) Mole fraction of H₂O is 0.8

18. 100 mL of 0.06 M Ca(NO₃)₂ is added to 50 mL of 0.06 M Na₂C₂O₄. After the reaction is complete (a) 0.003 moles of calcium oxalate will get precipitated

(b) 0.003 M of excess of Ca²⁺ will remain in excess (c) Na₂C₂O₄ is limiting reagent

(d) Ca(NO₃)₂ is excess reagent

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19. 0.1 M HCl is used to react with 1g of mixture of Na₂CO₃ and NaHCO₃ containing equimolar amount of two. The volume of HCl used is

(a) 156.0 mL (b) 0.156 L (c) 1.57 L (d) 15.7 L

20. H₃BO₃, Boric acid is

(a) Monobasic acid (b) Tribasic acid (c) Dibasic acid (d) Aprotic acid

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21. In the titration of K₂Cr₂O₇ and ferrous sulphate, following data is obtained V₁ mL of 1.0 M₁ K₂Cr₂O₇ requires

V₂ mL of 1.0 M₂FeSO₄

Which of the following relations is/are true for the above titration

(a) 6 M₁V₂ = M₂V₂ (b) M₁V₁ = 6 M₂V₂ (c) N₁V₁ = N₂V₂ (d) M₁V₁ = M₂V₂

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22. 10 volume H₂O₂ solution is present, then it means

(a) 10 ml of H₂O₂ solution liberates 1 ml of oxygen at STP (b) 1 ml of H2O2 solution liberates 10 ml of oxygen at STP (c) 0.0303 g of H₂O₂ in 10 ml of solution liberates 10 ml O₂at STP (d) 0.0303 g of H₂O₂ in 1 ml of the solution liberates 10 ml O₂ at STP

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23. Which of the following statements are correct

(a) 0.2 moles of KMnO₄ will oxidise one mole of ferrous ions to ferric ions in acidic medium (b) 1.5 moles of KMnO₄ will oxidise 1 mole of ferrous oxalate to ferric oxalate in acidic medium (c) 0.6 moles of KMnO₄ will oxidise 1 mole of ferrous oxalate to one mole of ferric ion and carbon

dioxide in acidic medium

(d) 1 mole of K₂Cr₂O₇ will oxidise 2 moles of ferrous oxalate to ferric ions and carbon dioxide in acidic medium

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24. Silver metal in ore is dissolved by potassium cyanide solution in the presence of air by the reaction (a) The amount of KCN required to dissolve 100 g of pure Ag is 120 g

(b) The amount of oxygen used in this process is 0.742 g (c) The amount of oxygen used in this process is 7.40 g (d) The volume of oxygen used at STP is 5.20 litres

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25. 16 ml of hydride of nitrogen were exploded in a eudiometric, tube and the volume after explosion was 32 ml. To this, 14 ml of oxygen were added and the mixture again was exploded.

On cooling, the volume of the residual gases was found to be 100 mL (a) The volume of the mixture before second explosion is 50 mL (b) The volume of the mixture before second explosion is 46 mL

(c) The residual gases measuring 10 mL is a mixture of N₂⁺ unreacted oxygen (d) The decrease in volume after second explosion is 36 mL

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Exercise

Iodine titrations: Compound containing iodine are widely used in titrations, commonly known as iodine titration. It is of two kinds

(i) Iodometric titrations (ii) Iodimetric titrations

(i) Iodometric titrations: It is nothing but an indirect method of estimating the iodine. In this type of titration, an oxidizing agent is made to react with excess of KI, in acidic medium or, basic medium in which I oxidizes into I⁻ ². Now the liberated I² can be titrated with Na²S²O³ solution.

Oxidi sin g agent→ →Na S O / H^{2 2 3} ⁺ ⁻+

2 2 4 6

KI I I Na S O

Although solid I² is black and insoluble in water, but it converts into soluble I³ ions

Starch is used as indicator near the end point or equivalence point. Even small amount of I² molecules, gives blue colour with starch. The completion of the reaction can be detected when blue colour disappears at the and point. In iodimetric titration, the strength of reducing agent is determined by reacting it with I².

1. When 79.75 g of CuSO⁴ sample containing inert impurity is reacted with KI, the liberated I² is reacted with 50 mL (1M) Na²S²O³ in basic medium, where it oxidizes into SO^4–2 ions, and I² reduces into I , ⁻ resulting solution is neutralized with K²CO³, then treated with excess of KI. The liberated I² required 2 mL M

10 Na²S²O³ in acidic solution, then what is the difference of the number of m mole of Cu⁺² and C²O^4–2ions in the solution?

(a) 40 (b) 10 (c) 30 (d) 50

4. When 1.66 g of KI is reacted with excess of KIO³ in presence of 6N HCl, then ICl is produced. The amount of KIO³ reacted and ICl formed are respectively.

(a) 4 × 10^–2 mole, 3 × 10^–3 mole (b) 1.5 × 10^–2 mole, 5 × 10^–3 mole (c) 5 × 10^–2 mole, 1.5 × 10^–3 mole (d) 5 × 10^–3 mole, 1.5 × 10^–2 mole

In document 01_Stoichiometry & Redox Reaction_final (Page 46-50)