Chemistry 9th Chap 11 : Topic 8 - Maryam Publications

Chemistry Chapter 11 : Topic 8

Catalytic Converters

1 / 18

During the combustion process in a car engine, nitrogen oxides (NOₓ) are formed mainly due to which condition?

A) Complete absence of oxygen during combustion

B) Low temperature combustion of fuel

C) Presence of carbon monoxide in fuel tank

D) Reaction of nitrogen and oxygen at high temperature inside engine cylinders

2 / 18

Why are nitrogen oxides (NOₓ) not formed significantly at room temperature in air?

A) Carbon monoxide prevents their formation

B) Nitrogen is chemically inert and does not react easily at low temperatures

C) Fuel blocks the reaction completely

D) Oxygen is completely absent in air

3 / 18

Which gases are mainly responsible for forming acid rain when released from vehicle exhausts?

A) Nitrogen oxides and sulfur dioxide

B) Carbon dioxide and methane

C) Oxygen and nitrogen

D) Hydrogen and helium

4 / 18

In car engines, nitrogen oxides are produced due to:

A) Reaction between fuel and nitrogen in petrol

B) Decomposition of carbon dioxide

C) High-temperature reaction between atmospheric nitrogen and oxygen

D) Burning of lubricating oil only

5 / 18

What is the main function of a catalytic converter in a car exhaust system?

A) Convert toxic gases into less harmful gases

B) Increase engine speed

C) Store exhaust gases temporarily

D) Increase fuel efficiency by adding oxygen

6 / 18

Which of the following reactions correctly represents removal of nitrogen oxides in a catalytic converter?

A) 2NO → N₂+O₂ (catalyzed reduction)

B) NO+O₂ → NO₂

C) CO₂ → CO+O₂

D) CO+NO → CO₂+N

7 / 18

In the reaction: CO+2NO → CO₂+N₂, the role of CO is:

A) Inert gas

B) Oxidizing agent

C) Reducing agent

D) Catalyst

8 / 18

Which metals are commonly used in catalytic converters?

A) Platinum, palladium and rhodium

B) Iron and copper

C) Sodium and potassium

D) Zinc and magnesium

9 / 18

What is the main environmental problem caused by NOₓ gases?

A) Global cooling only

B) Increase in oxygen concentration

C) Formation of smog and acid rain

D) Decrease in atmospheric pressure

10 / 18

Why is a catalytic converter installed near the engine exhaust?

A) To cool exhaust gases completely

B) To ensure high temperature for efficient catalytic reactions

C) To increase fuel combustion

D) To store gases temporarily

11 / 18

Which gases are primarily converted into less harmful products in a three-way catalytic converter?

A) O₂, N₂ and H₂

B) CO₂, H₂O and O₂

C) N₂, He and Ar

D) CO, NOₓ and hydrocarbons

12 / 18

Which statement correctly describes nitrogen oxides?

A) They are used as fuel in engines.

B) They are harmless gases released in small amounts.

C) They are formed only in laboratories.

D) They are toxic pollutants formed during high-temperature combustion.

13 / 18

In catalytic converters, NO is converted mainly into:

A) O₂

B) NO₂

C) N₂

D) NH₃

14 / 18

What happens to carbon monoxide in a catalytic converter?

A) It remains unchanged.

B) It is oxidized to carbon dioxide.

C) It is reduced to carbon.

D) It forms methane.

15 / 18

Why is nitrogen normally unreactive in air but becomes reactive in engines?

A) Due to presence of catalysts in air.

B) Because nitrogen becomes liquid in engines.

C) Due to extremely high temperature in engine cylinders.

D) Because pressure decreases in engines.

16 / 18

Which of the following best describes the overall purpose of a catalytic converter?

A) Convert harmful exhaust gases into less harmful gases before release

B) Separate nitrogen from air

C) Increase engine power output

D) Store fuel for combustion

17 / 18

What is the correct environmental benefit of reducing NOₓ emissions?

A) Increased oxygen toxicity

B) Increased fuel consumption

C) Increased rainfall acidity

D) Reduced formation of smog and acid rain

18 / 18

The reaction CO+2NO → CO₂+N₂ is an example of:

A) Neutralization reaction

B) Decomposition reaction

C) Precipitation reaction

D) Redox reaction

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