Indicate whether the following statements are True or False. Also, write the false statements in their correct form.
(a) Air is necessary for combustion.
(b) Magnesium is a non-combustible metal.
(c) Carbon dioxide is an excellent fire extinguisher.
(d) Calorific value of wood is higher than that of coal.
(a) Air is necessary for combustion.
(b) Magnesium is a non-combustible metal.
(c) Carbon dioxide is an excellent fire extinguisher.
(d) Calorific value of wood is higher than that of coal.
(a) Burning substances in the presence of air is called as combustion. That is, during combustion, a substance reacts with oxygen (from air) to give off heat. Therefore, air is necessary for combustion.
Hence, the given statement is true.
(b)
When a piece of magnesium ribbon is ignited, light and heat are produced. That is, magnesium reacts with oxygen to form a compound called magnesium oxide along with the production of heat and light. The chemical equation for the given reaction can be given as,
2Mg+O2→2MgO+Heat + Light
Hence, the given statement is false. It can be corrected as,
Magnesium is a combustible material.
(c) Carbon dioxide does not support burning. It is the best fire extinguisher to put off fires caused by burning. That is, it can cut off the supply of air (oxygen) which helps in extinguishing the fire.
Therefore, the given statement is true.
(d) Calorific value of a fuel is the amount of heat energy produced on complete combustion of 1 kg of the fuel. It is expressed in the unit called kilojoule per kg (kJ/kg). The calorific value of wood is 17000-22000 kJ/ kg and that of coal is 25000-33000 kJ/ kg. Coal has a higher calorific value than wood.
Hence, the given statement is false.
It can be corrected as,
Calorific value of coal is higher than that of wood.
Hence, the given statement is true.
(b)
When a piece of magnesium ribbon is ignited, light and heat are produced. That is, magnesium reacts with oxygen to form a compound called magnesium oxide along with the production of heat and light. The chemical equation for the given reaction can be given as,
2Mg+O2→2MgO+Heat + Light
Hence, the given statement is false. It can be corrected as,
Magnesium is a combustible material.
Therefore, the given statement is true.
(d) Calorific value of a fuel is the amount of heat energy produced on complete combustion of 1 kg of the fuel. It is expressed in the unit called kilojoule per kg (kJ/kg). The calorific value of wood is 17000-22000 kJ/ kg and that of coal is 25000-33000 kJ/ kg. Coal has a higher calorific value than wood.
Hence, the given statement is false.
It can be corrected as,
Calorific value of coal is higher than that of wood.
