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

C) Presence of carbon monoxide in fuel tank

D) Low temperature combustion of fuel

2 / 18

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

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

B) Carbon monoxide prevents their formation

C) Oxygen is completely absent in air

D) Fuel blocks the reaction completely

3 / 18

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

A) Oxygen and nitrogen

B) Carbon dioxide and methane

C) Nitrogen oxides and sulfur dioxide

D) Hydrogen and helium

4 / 18

In car engines, nitrogen oxides are produced due to:

A) High-temperature reaction between atmospheric nitrogen and oxygen

B) Reaction between fuel and nitrogen in petrol

C) Decomposition of carbon dioxide

D) Burning of lubricating oil only

5 / 18

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

A) Increase engine speed

B) Convert toxic gases into less harmful gases

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) CO+NO → CO₂+N

B) 2NO → N₂+O₂ (catalyzed reduction)

C) NO+O₂ → NO₂

D) CO₂ → CO+O₂

7 / 18

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

A) Catalyst

B) Reducing agent

C) Inert gas

D) Oxidizing agent

8 / 18

Which metals are commonly used in catalytic converters?

A) Platinum, palladium and rhodium

B) Sodium and potassium

C) Zinc and magnesium

D) Iron and copper

9 / 18

What is the main environmental problem caused by NOₓ gases?

A) Decrease in atmospheric pressure

B) Increase in oxygen concentration

C) Global cooling only

D) Formation of smog and acid rain

10 / 18

Why is a catalytic converter installed near the engine exhaust?

A) To cool exhaust gases completely

B) To increase fuel combustion

C) To store gases temporarily

D) To ensure high temperature for efficient catalytic reactions

11 / 18

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

A) O₂, N₂ and H₂

B) N₂, He and Ar

C) CO₂, H₂O and O₂

D) CO, NOₓ and hydrocarbons

12 / 18

Which statement correctly describes nitrogen oxides?

A) They are used as fuel in engines.

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

C) They are harmless gases released in small amounts.

D) They are formed only in laboratories.

13 / 18

In catalytic converters, NO is converted mainly into:

A) N₂

B) NO₂

C) NH₃

D) O₂

14 / 18

What happens to carbon monoxide in a catalytic converter?

A) It remains unchanged.

B) It is reduced to carbon.

C) It is oxidized to carbon dioxide.

D) It forms methane.

15 / 18

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

A) Because nitrogen becomes liquid in engines.

B) Due to extremely high temperature in engine cylinders.

C) Due to presence of catalysts in air.

D) Because pressure decreases in engines.

16 / 18

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

A) Store fuel for combustion

B) Separate nitrogen from air

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

D) Increase engine power output

17 / 18

What is the correct environmental benefit of reducing NOₓ emissions?

A) Increased fuel consumption

B) Increased oxygen toxicity

C) Reduced formation of smog and acid rain

D) Increased rainfall acidity

18 / 18

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

A) Neutralization reaction

B) Redox reaction

C) Decomposition reaction

D) Precipitation reaction

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