Fuels, Combustion and Flame Worksheet-9

Fuels, Combustion and Flame Worksheet-9

1. L.P.G used as domestic fuel is mixed with a strong smelling volatile liquid for:

(a) better combustion                 (b) good smell/fragrance

(c) detection of gas leakage        (d) higher calorific value

2. Hydrogen gas has the highest calorific value i.e., 150 kJ/kg yet it is not used as a fuel. The reasons are:

(a) it is explosive in nature

(b) it causes storage problem

(c) it causes transportation problem

(d) all of these

3. When wood is used as fuel in chullahs, gaps are left in between the logs of wood. This is done for:

(a) movement of air                     (b) less consumption of wood

(c) to control temperature         (d) none of these

4. For a spontaneous combustion to take place:

(a) flame is required

(b) spark is replied

(c) rise in temperature to ignition temperature is required

(d) nothing is required

5. An electric spark is struck between two electrodes placed near each other, inside a closed tank full of petrol. What will happen?

(a) Spontaneous combustion of petrol

(b) Explosion

(c) Slow combustion of petrol

(d) Nothing will happen

6. Which of the following statement is NOT true?

(a) Flame can be seen over burning solids and liquids

(b) Type of flame depends upon the amount of oxygen available

(c) Invisible zone of a flame is the least hot zone

(d) Blue zone indicates complete combustion of fuel

7. When water is poured over burning wood, the fire goes off. This is because:

(a) temperature of wood decreases

(b) temperature of water goes up

(c) molecules of water reacts with oxygen present in the flame

(d) the flame vapourises

8. A burning candle when placed in an enclosed jar immediately gets extinguished. This is because

(a) The supply of CO₂ is cut off

(b) The supply of O₂ is cut off

(c) The supply of N₂ is cut off

9. Good fuels have

(a) Low ignition temperature and high calorific value

(b) Low ignition temperature and low calorific value

(c) High ignition temperature and high calorific value

(d) High ignition temperature and low calorific value

10. When the LPG gas stove at home gives a yellow flame, it implies that

(a) The fuel undergoes complete combustion

(b) The fuel on burning gives yellow burnt particles

(c) The fuel undergoes partial combustion

(d) None of these

Answer Key:

(1)-(c); (2)-(d); (3)-(a); (4)-(c); (5)-(d); (6)-(c); (7)-(a); (8)-(b); (9)-(a); (10)-(c)