Chemistry MCQ Questions with Answer for all Competitive Exams

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Chemistry MCQ Questions with Answer

Q61. Which one of the following carbon compounds will not give a sooty flame?​​​

​(a)​ Benzene ​

(b)​ Hexane ​

(c)​ Naphthalene

​(d)​ Anthracene

Answer: ​(b)​

Explanation: Hexane does not give sooty flame as it is an alkane and the saturated compound whereas Benzene, Naphthalene, and Anthracene are aromatic and unsaturated so they give sooty flame.

Q62. Consider the following statements:

Coke is one of the materials of the charge added to blast furnace for the production of steel/iron. Its function is to

1. Act as the reducing agent
2. Remove silica associated with the iron ore
3. Function as fuel; to supply heat
4. Act as an oxidizing agent

Of these statements

(a) 1 and 2 are correct

(b) 2 and 4 are correct

(c) 1 and 3 are correct

(d) 3 and 4 are correct

Answer: (c)

Explanation: Coke is added to the blast furnace along with iron ore in a blast furnace. Coke being derived from fossil fuel by destructive distillation. Thus it contains a higher percentage of carbon and has a high calorific value that’s why it functions as a fuel to supply heat. Coke also acts as a reducing agent and reduces metal (iron) oxide to metal.

Chemical equations involved in the process are the following:

2C(s) + O2 (g) →2CO (g)

FeO(s) + CO (g) → Fe(s) + CO2 (g)

Fe2O3 + 3CO (g) → 2Fe(s) + 3CO2 (g)

Q63. Ammonia (NH3) obtained from different sources always has the same proportion of Nitrogen and Hydrogen. It proves the validity of the law of:

(a)​ Reciprocal proportion

​(b)​ Constant proportion

​(c) ​Multiple proportions ​

(d)​ None of the above

Answer: (b)​

Explanation: Ammonia (NH3) obtained from different sources always has the same proportion of Nitrogen and Hydrogen and it proves the validity of the law of constant proportion.

Q64. An aqueous solution of copper sulfate is acidic in nature because the salt undergoes

(a) Dialysis

(b) Electrolysis

(c) Hydrolysis

(d) Photolysis

Answer: (c)

Explanation: Aqueous solution of copper sulfate is acidic in nature because copper sulfate on dissolving with water, the following chemical reaction takes place

CuSO4 (s) + 2H2O → Cu(OH)2 (l) + H2SO4 (aq)

Now as we can see in the above chemical equation the sulphuric acid generated is strong mineral acid which results in an increase in the acidity of the solution. Thus the aqueous solution of copper sulfate is acidic in nature.

Q65. Protons and neutrons are bound in a nucleus by the ​

(a)​ Short-range ‘weak interaction’​ ​

(b) ​Short range ‘strong interaction’

​(c)​ Long range ‘electromagnetic interaction’

​(d) ​Long range ‘gravitational interaction’

Answer: ​(b) ​

Explanation: The force between protons and neutrons in the nucleus is short-range strong interaction.

Q66. An atom of carbon has 6 protons. Its mass number is 12. How many neutrons are present in an atom of carbon?​​​​​​​

​(a)​ 12

​(b)​ 6 ​

(c)​10

​(d)​ 14

Answer: ​(b)​

Explanation: Mass number = number of proton + number of neutron ​​

12 = 6+number of neutron ​​

12 – 6 = number of neutron

∴ Number of neutron= 6

Q67. Which one of the following statements is correct? ​

(a)​ Rutherford’s alpha-particle scattering experiment led to the discovery of the electron ​

(b)​ J J Thomson suggested that the nucleus of an atom contains protons ​

(c)​ The atomic number of an element is the same as the number of protons in the nucleus of its atom

​(d)​ The mass number of an atom is equal to the number of electrons in its shells Radioactivity: α, β, γ rays & Nuclear Fission & Fusion

Answer: (c)​

Explanation: In any atom, the atomic number represents the number of electrons which is equal to the number of protons.

Q68. Food cans are coated with tin and not with zinc because ​

(a)​ Zinc is costlier than tin ​

(b) ​Zinc has a higher melting point than tin ​

(c)​ Zinc is more reactive than tin

​(d)​ Zinc is less reactive than tin

Answer: ​(c)

Explanation: ​Zinc is much more reactive as compared to the tin and may react with natural acids and bases in food materials.

Q69. Sodium carbonate is basic salt because it is a salt of:

(a) Weak acid and weak base

(b) Strong acid and strong base

(c) Weak acid and strong base

(d) Strong acid and weak base

Answer: (c)

Explanation: Sodium carbonate is basic salt because it is a salt of a weak acid and a strong base.

H2CO3 + 2NaOH → Na2CO3 + 2H2O

Q70. While tinning of brass utensils, the ammonium chloride powder used to clean the hot utensil produces fumes of ​

(a)​ Ammonia ​

(b) ​Carbon monoxide ​

(c) ​Hydrochloric acid

​(d)​ Ammonia and hydrochloric acid

Answer: ​(d) ​

Explanation: Ammonium chloride decomposes into ammonia and hydrogen chloride gas.

​​NH4Cl → NH3 + HCl

It produces fumes of ammonia and hydrochloric acid.

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