Chemistry 9th Chap 7 : Topic 1 - Maryam Publications

Chemistry Chapter 7 : Topic 1

Redox Reactions

1 / 17

In a chemical reaction where a substance gains oxygen while another substance loses oxygen at the same time, the reaction is best described as:

A) Redox reaction

B) Neutralization reaction

C) Decomposition reaction

D) Displacement reaction

2 / 17

A reaction is given as: CuO + H₂ → Cu + H₂O

A) Both copper and hydrogen are oxidized

B) Hydrogen is oxidized and copper oxide is reduced

C) Copper is oxidized and hydrogen is reduced

D) No oxidation or reduction occurs

3 / 17

Which of the following correctly defines oxidation in terms of electrons?

A) Gain of neutrons

B) Loss of electrons

C) Loss of protons

D) Gain of electrons

4 / 17

In a redox reaction, oxidation and reduction always occur:

A) Only in presence of light

B) In separate reactions

C) Simultaneously

D) At different times

5 / 17

In the reaction: Zn + Cu²⁺ → Zn²⁺ + Cu

A) Zn

B) Cu²⁺

C) Cu

D) Zn²⁺

6 / 17

Which of the following represents reduction in terms of hydrogen?

A) Loss of hydrogen

B) Increase in oxidation number

C) Gain of oxygen

D) Gain of hydrogen

7 / 17

Consider the reaction: 2Mg + O₂ → 2MgO

A) It gains electrons and is reduced

B) It gains oxygen and is oxidized

C) It loses oxygen and is reduced

D) It remains unchanged

8 / 17

Which statement best describes a redox reaction?

A) Only oxidation occurs

B) No change in oxidation states occurs

C) Only reduction occurs

D) Electron transfer takes place between substances

9 / 17

In the reaction: H₂ + Cl₂ → 2HCl

A) No electron transfer occurs

B) Hydrogen is oxidized and chlorine is reduced

C) Chlorine is oxidized and hydrogen is reduced

D) Both are oxidized

10 / 17

Oxidation state increases when a substance:

A) Gains neutrons

B) Gains hydrogen only

C) Gains electrons

D) Loses electrons

11 / 17

A reaction where oxygen is removed from a compound is called:

A) Neutralization

B) Oxidation

C) Hydrolysis

D) Reduction

12 / 17

Which of the following is TRUE about redox reactions?

A) Only one substance changes oxidation state

B) No change in chemical composition occurs

C) Both oxidation and reduction occur in different reactions

D) Electron transfer is involved

13 / 17

In terms of oxygen, oxidation means:

A) Loss of electrons only

B) Gain of hydrogen

C) Loss of oxygen

D) Gain of oxygen

14 / 17

In the reaction: Fe₂O₃ + 3CO → 2Fe + 3CO₂

A) Both are oxidized

B) No change occurs

C) Fe₂O₃ is oxidized and CO is reduced

D) Fe₂O₃ is reduced and CO is oxidized

15 / 17

Which statement best explains oxidation and reduction in terms of electrons?

A) Oxidation is gain of electrons, reduction is loss of electrons

B) Both involve gain of electrons

C) Both involve loss of electrons

D) Oxidation is loss of electrons, reduction is gain of electrons

16 / 17

Which of the following is NOT a feature of a redox reaction?

A) Only one reactant changes

B) Simultaneous oxidation and reduction

C) Electron transfer

D) Change in oxidation state

17 / 17

In redox reactions, the substance that causes another substance to be oxidized is called:

A) Reducing agent

B) Catalyst

C) Product

D) Oxidizing agent

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