Redox reactions Quiz | Chemistry Quiz
Redox-reactions
(i) An overall reaction in which oxidation and reduction take place simultaneously is called redox or oxidation-reduction reaction. These reactions involve the transfer of electrons from one atom to another. Thus every redox reaction is made up of two half-reactions; One-half reaction represents the oxidation and the other half-reaction represents the reduction.
(ii) Types of redox reaction
(a) Direct redox reaction: The reactions in which oxidation and reduction take place in the same vessel are called direct redox reactions.
(b) Indirect redox reaction: The reactions in which oxidation and reduction take place in different vessels are called indirect redox reactions. Indirect redox reactions are the basis of electrochemical cells.
(c) Intermolecular redox reactions: In which one substance is oxidized while the other is reduced.
Oxidizing and Reducing agents
(1) Definition: The substance (atom, ion or molecule) that gains electrons and is thereby reduced to a low valency state is called an oxidizing agent, while the substance that loses electrons and is thereby oxidized to a higher valency state is called a reducing agent.
Or
An oxidizing agent is a substance, the oxidation number of whose atom or atoms decreases while a reducing agent is a substance the oxidation number of whose atom increases.
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Oxidation, Reduction Quiz
1. Oxidation involves
(a) Loss of electrons
(b) Gain of electrons
(c) Increase in the valency of negative part
(d) Decrease in the valency of positive part
SOL: (a) It is the process in which electrons are lost (de-electronation).
2. The solution of sodium metal in liquid ammonia is strongly reducing due to the presence of the following in the solution
(a) Sodium atoms
(b) Solvated electrons
(c) Sodium hydride
(d) Sodium amide
SOL: B
Oxidizing and Reducing agent Quiz
3. A reducing agent is a substance which can
(a) Accept electron
(b) Donate electrons
(c) Accept protons
(d) Donate protons
SOL: (b) A substance that is capable of reducing other substances and is capable of donating electrons during reduction is called a reducing agent or reductant.
4. When NaCl is dissolved in water the sodium ion becomes
(a) Oxidised (b) Reduced
(c) Hydrolysed (d) Hydrated
SOL: (d)
5. The strongest reducing agent is
(a) K (b) Mg
(c) Al (d) Br
SOL: (a) Potassium has higher negative value of reduction potential hence it shows more reducing properties.
6. H2O2 is used as
(a) An oxidant only
(b) A reductant only
(c) An acid only
(d) An oxidant, a reductant and an acid
SOL: (c) Because I2 is a reducing agent.
Oxidation number and Oxidation state Quiz
7. The oxidation number of chlorine in HOCl
(a) – 1 (b) 0
(c) + 1 (d) + 2
SOL: (c) In hypochlorous acid chlorine atom has + 1 oxidation number.
8. Maximum oxidation state of Cr is
(a) 3 (b) 4
(c) 6 (d) 7
SOL: (c) Maximum oxi. state for Cr is + 6.
9. The oxidation state of elemental carbon is
(a) 0 (b) 1
(c) 2 (d) 3
SOL: (a) Every element always shows zero oxidation state.
10. The oxidation number of carbon in CH2O is
(a) – 2 (b) + 2
(c) 0 (d) + 4
SOL: (c)
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11. The oxidation state of oxygen in F2O is
(a) + 1 (b) + 2
(c) (d)
SOL: (b) Oxygen shows + 2 oxidation state in F2O. As most electronegative element, it always has an O. No. =–1
12. Phosphorus has the oxidation state of +3 in
(a) Orthophosphoric acid (b) Phosphorus acid
(c) Metaphosphoric acid (d) Pyrophosphoric acid
SOL: (b)
13. The most common oxidation state of an element is –2. The number of electrons present in its outermost shell is
(a) 4 (b) 2
(c) 6 (d) 8
SOL: (c) Oxygen has 6 electrons in the outer most shell and shows common oxidation state – 2.
Redox reaction and Method for balancing Quiz
Redox reaction Quiz
14. Starch paper is used to test for the presence of
(a) Iodine
(b) Oxidising agent
(c) Iodide ion
(d) Reducing agent
SOL: (a)
15. The number of moles of KMnO4 reduced by one mole of
KI in alkaline medium is:
(a) One fifth (b) five
(c) One (d) Two
SOL: (d)In alkaline medium
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Auto oxidation and Disproportionation Quiz
16. Which one of the following nitrates will leave behind a metal on strong heating
(a) Ferric nitrate (b) Copper nitrate
(c) Manganese nitrate (d) Silver nitrate
SOL: (d)
.
17. To prevent rancidification of food material, which of the following is added
(a) Reducing agent (b) Anti-oxidant
(c) Oxidising agent (d) None of these
SOL: (b) To prevent rancidification of food material we add anti-oxidant which are called oxidation inhibitor.
18. Prevention of corrosion of iron by zinc coating is called
(a) Galvanization
(b) Cathodic protection
(c) Electrolysis
(d) Photo–electrolysis
SOL: A