Test: Combustion And Flame - 3


20 Questions MCQ Test General Science(Prelims) by IRS Divey Sethi | Test: Combustion And Flame - 3


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QUESTION: 1

What are the two main hydrocarbons present in L.P.G.?

Solution:

L.P.G. is a mixture of hydrocarbons. It consists of butane, propane and ethane but butane and propane are the two major constituents of L.P.G.

QUESTION: 2

What is the heat produced by burning 1 g of fuel completely known as?

Solution:

Calorific value of a substance is the amount of heat released during the combustion of a specified amount of fuel or food. The calorific value is the characteristic of a substance.

QUESTION: 3

Which of the following has the highest calorific value?

Solution:

Natural gas has the highest calorific value of 50000 kJ/kg Petrol has 45000 kJ/kg Kerosene has 45000 kJ/kg and Coke has 28000 kJ/kg

QUESTION: 4

Which of the following has the characteristics of a good fuel?

Solution:

All the given substances can act as fuels but butane is considered as a good fuel because of the following characteristics:
(i) Exists in gaseous state
(ii) Has high calorific value
(iii) Does not form poisonous products during combustion

QUESTION: 5

What is burning of a substance in the presence of air with the evolution of heat called?

Solution:

The process of a substance burning in the presence of air with evolution of heat is called combustion.

QUESTION: 6

When methane burns in air, what are the products formed?

Solution:

Fuels and hydrocarbons burn in oxygen and form 

CO2+2O2→CO2+2H2O+heat

and give out heat. 

CH4+2O2→CO2+2H2O+heat

QUESTION: 7

What kind of reaction is combustion?

Solution:

Combustion is an oxidation reaction accompanied by heat and light.

QUESTION: 8

Which of the following is a non- combustible substance?

Solution:

Diamond is a non-combustible substance.

QUESTION: 9

What is the lowest temperature at which a substance starts burning called?

Solution:

The temperature at which a substance starts burning on heating is called ignition temperature. Highly    inflammable substances have a low ignition temperature. Hence, they catch fire easily.

QUESTION: 10

If the temperature falls below its ignition temperature, then what happens to the burning substance?

Solution:

A burning substance will be extinguished if the temperature falls below its ignition temperature.

QUESTION: 11

Which of the following is an example of rapid combustion?

Solution:

Rapid combustion is a form of combustion in which large amounts of heat and light energy are released. Candle shows rapid combustion, whereas cracker and white Phosphorous come under explosion and spontaneous combustion respectively.

QUESTION: 12

In which of the following types of combustion are heat, light and sound produced?

Solution:

The combustion in which heat, light and sound are produced is known as explosive combustion.

QUESTION: 13

I Match the entries in Column-l with those in Column-ll correctly.

Solution:

The correct combination is a - 3, b - 4, c - 2, d - 1
(i) Dark inner zone -Unburnt vapours of wax
(ii) Blue zone - Complete combustion
(iii) Luminous zone ? Partial combustion
(iv) Non-luminous zone - Hottest part (no carbon)

QUESTION: 14

What does the blue zone in an L.P.G. flame indicate?

Solution:

The blue zone in L.P.G. flame indicates the hottest zone where complete combustion takes place.

QUESTION: 15

What does natural gas contain?

Solution:

Natural gas consists of methane, ethane, propane etc., of which methane forms major composition of about 95%.

QUESTION: 16

How is synthetic petrol produced?

Solution:

The Bergius Process is a very simple process for converting brown coal completely into crude oil. It was invented by Dr. Friedrich Bergius. In this process, brown coal, also known as lignite is powdered and mixed with heavy oil and heated with hydrogen under high pressure of about 200-250 atm. and a temperature of about 748 K in the presence of iron oxide as catalyst. The vapours on condensation give a liquid resembling crude oil. This is called synthetic petrol, which on fractional distillation gives petrol (gasoline).

QUESTION: 17

Arrange the following fuels in the increasing order of their calorific value.

(i) Petrol
(ii) Wood
(iii) Coal
(iv) Natural gas

Solution:

(i) Wood - 17000 to 22000 kJ/kg
(ii) Coal - 25000 to 33000 kJ/kg
(iii) Petrol - 45000 kJ/kg
(iv) Natural gas - 50000 kJ/kg
The correct order of the increasing order of calorific values is: (ii), (iii), (i), (iv).

QUESTION: 18

What does the incomplete combustion of a fuel give?

Solution:

When a fuel (carbon) undergoes incomplete combustion, carbon monoxide is formed. It is a poisonous gas and fatal, if inhaled.

QUESTION: 19

The total amount of heat produced by a fuel having a calorific value of 20 kJ kg 1 was found to be 50,000 joules. How much fuel was burnt?

Solution:

1 kg of fuel when burnt gives 20,000 joules of heat energy. 50,000 joules of heat energy will be produced by 2.5 kg of fuel as given below. 1 kg fuel produces 20kJkg−1 heat ? fuel produces 50kJkg−1 heat 

QUESTION: 20

What is combustion?

Solution:

Combustion is burning of a substance in the presence of oxygen. During this process heat energy is released, it is therefore an oxidation and exothermic reaction.

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