Question 1 

Assign oxidation number to the underlined elements in each of the following species:
(a) NaH₂PO₄
(b) NaHSO₄
(c) H₄P₂O₇
(d) K₂MnO₄
(e) CaO₂
(f) NaBH₄
(g) H₂S₂O₇
(h) KAl(SO₄)₂.12 H₂O

Question 2  

What are the oxidation number of the underlined elements in each of the following and how do you rationalise your results ?
(a) KI₃
(b) H₂S₄O₆
(c) Fe₃O₄
(d) CH₃CH₂OH
(e) CH₃COOH

Question 3

 Justify that the following reactions are redox reactions:
(a) CuO_(s) + H_2(g) → Cu_(s) + H₂O_(g)
(b) Fe₂O_3(s) + 3CO_(g) → 2Fe_(s) + 3CO_2(g)
(c) 4BCl_3(g) + 3LiAlH_4(s) → 2B₂H_6(g) + 3LiCl_(s) + 3 AlCl_{3 (s)}
(d) 2K_(s) + F_2(g) → 2K⁺F^– _(s)
(e) 4 NH_3(g) + 5 O_2(g) → 4NO_(g) + 6H₂O_(g)

Question 4

 Fluorine reacts with ice and results in the change:
H₂O_(s) + F_2(g) → HF_(g) + HOF_(g)
Justify that this reaction is a redox reaction.

Question 6

Write the formulae for the following compounds:
(a) Mercury(II) chloride
(b) Nickel(II) sulphate
(c) Tin(IV) oxide
(d) Thallium(I) sulphate
(e) Iron(III) sulphate
(f) Chromium(III) oxide

Question 8

While sulphur dioxide and hydrogen peroxide can act as oxidising as well as reducing agents in their reactions, ozone and nitric acid act only as oxidants. Why?

Question 9

Consider the reactions:
(a) 6CO_2(g) + 6H₂O_(l) → C₆H₁₂O_6(aq) + 6O_2(g)
(b) O_3(g) + H₂O_2(l) → H₂O_(l) + 2O_2(g)
Why it is more appropriate to write these reactions as:
(a) 6CO_2(g) + 12H₂O_(l) → C₆H₁₂O_6(aq) + 6H₂O_(l) + 6O_2(g)
(b) O_3(g) + H₂O_2(l) → H₂O_(l) + O_2(g) + O_2(g)
Also suggest a technique to investigate the path of the above (a) and (b) redox reactions.

Question 10

The compound AgF₂ is an unstable compound. However, if formed, the compound acts as a very strong oxidizing agent. Why?

Question 12
How do you count for the following observations?
(a) Though alkaline potassium permanganate and acidic potassium permanganate both are used as oxidants, yet in the manufacture of benzoic acid from toluene we use alcoholic potassium permanganate as an oxidant. Why? Write a balanced redox equation for the reaction.
(b) When concentrated sulphuric acid is added to an inorganic mixture containing chloride, we get colourless pungent smelling gas HCl, but if the mixture contains bromide then we get red vapour of bromine. Why?

Question 13
Identify the substance oxidised, reduced, oxidising agent and reducing agent for each of the following reactions:
(a) 2AgBr _(s) + C₆H₆O_2(aq) → 2Ag_(s) + 2HBr _(aq) + C₆H₄O_2(aq)
 
(b) HCHO_(l) + 2[Ag (NH₃)₂]⁺_(aq) + 3OH^-_(aq) → 2Ag_(s) + HCOO^-_(aq) + 4NH_3(aq) + 2H₂O_(l)
 
(c) HCHO _(l) + 2Cu²⁺_(aq) + 5 OH^-_(aq) → Cu₂O_(s) + HCOO^-_(aq) + 3H₂O_(l)
 
(d) N₂H_4(l) + 2H₂O_2(l) → N_2(g) + 4H₂O_(l)
 
(e) Pb_(s) + PbO_2(s) + 2H₂SO_4(aq) → 2PbSO_4(s) + 2H₂O_(l)

Question 14
Consider the reactions :
2 S₂O^2– _{3 (aq)} + I_2(s) → S₄ O^2– _6(aq) + 2I ^– _(aq)
S₂O^2– _3(aq) + 2Br_2(l) + 5 H₂O_(l) → 2SO^2–_4(aq) + 4Br^–_(aq) + 10H⁺_(aq)
Why does the same reductant, thiosulphate react differently with iodine and bromine ?

Question 16
Why does the following reaction occur ?
XeO^4– _6(aq)  +  2F ^– _(aq) + 6H ⁺ _(aq)  →   XeO_3(g)  +  F_2(g) + 3H₂O_(l)
What conclusion about the compound Na₄XeO₆ (of which XeO^4– 6 is a part) can be drawn from the reaction.

Question 17
Consider the reactions:
(a) H₃PO_2(aq) + 4 AgNO_3(aq) + 2 H₂O_(l) → H₃PO_4(aq) + 4Ag_(s) + 4HNO_3(aq)
 
(b) H₃PO_2(aq) + 2CuSO_4(aq) + 2 H₂O_(l) → H₃PO_4(aq) + 2Cu_(s) + H₂SO_4(aq)
 
(c) C₆H₅CHO_(l) + 2 [Ag (NH₃)₂]⁺_(aq) + 3OH^-_(aq) → C₆H₅COO^-_(aq) + 2Ag_(s) + 4NH_3(aq) + 2 H₂O_(l)
 
(d) C₆H₅CHO_(l) + 2Cu²⁺_(aq) + 5OH^-_(aq) → No change observed.
 
What inference do you draw about the behaviour of Ag⁺and Cu²⁺from these reactions?

Question 18
Balance the following redox reactions by ion – electron method :
(a) MnO₄ ^– (aq) + I ^– (aq) → MnO_{2 (s)} + I_2(s) (in basic medium)
(b) MnO₄ ^– (aq) + SO_{2 (g)} → Mn²⁺ (aq) + HSO₄^– (aq) (in acidic solution)
(c) H₂O_{2 (aq)} + Fe ²⁺ (aq) → Fe³⁺ (aq) + H₂O (l) (in acidic solution)
(d) Cr₂O₇ ^2– + SO_2(g) → Cr³⁺ _(aq) + SO₄^2– (aq) (in acidic solution)

Question 20
What sorts of informations can you draw from the following reaction ?
(CN)_2(g)  +  2OH^-_(aq)  →  CN^-_(aq) + CNO^-_(aq) + H₂O_(l)

Question 22
Consider the elements:
Cs, Ne, I and F
(a) Identify the element that exhibits only negative oxidation state.
(b) Identify the element that exhibits only postive oxidation state.
(c) Identify the element that exhibits both positive and negative oxidation states.
(d) Identify the element which exhibits neither the negative nor does the positive oxidation state.

Question 24
Refer to the periodic table given in your book and now answer the following questions:
(a) Select the possible non metals that can show disproportionation reaction.
(b) Select three metals that can show disproportionation reaction.

Question 25
In Ostwald's process for the manufacture of nitric acid, the first step involves the oxidation of ammonia gas by oxygen gas to give nitric oxide gas and steam. What is the maximum weight of nitric oxide that can be obtained starting only with 10.00 g. of ammonia and 20.00 g of oxygen?

Question 26
Using the standard electrode potentials given in the Table 8.1, predict if the reaction between the following is feasible:
(a) Fe³⁺(aq) and I^-(aq)
(b) Ag⁺(aq) and Cu_(s)
(c) Fe³⁺ (aq) and Cu_(s)
(d) Ag(s) and Fe³⁺(aq)
(e) Br²(aq) and Fe²⁺(aq)

Question 27
Predict the products of electrolysis in each of the following:
(i) An aqueous solution of AgNO₃ with silver electrodes
(ii) An aqueous solution AgNO₃ with platinum electrodes
(iii) A dilute solution of H₂SO₄ with platinum electrodes
(iv) An aqueous solution of CuCl₂ with platinum electrodes.

Question 30
Depict the galvanic cell in which the reaction Zn(s) + 2Ag⁺(aq) → Zn²⁺(aq) + 2Ag(s) takes place, further show:
(i) which of the electrode is negatively charged,
(ii) the carriers of the current in the cell, and
(iii) individual reaction at each electrode.