Differentiate between –
i) Corrosion and Rancidity
ii) Calcination and Roasting
Differentiate between –
i) Corrosion and Rancidity
ii) Calcination and Roasting
i) CORROSION: - The slow destruction of metals by the action of moisture and air on the metal is called corrosion.
Eg: - rusting of iron, green layer above copper etc.
Prevention of corrosion – Galvanization is a method of protecting steel and iron from rusting by coating them with a thin layer of zinc.
RANCIDITY: - The degradation of fats and oils by getting oxidized or by the action of Oxygen upon them is called rancidity.
Eg: - An unusual smell coming out of chips after their expiry, etc.
Prevention of rancidity- Usually substances which prevent oxidation (antioxidants) are added to foods containing fats and oil. Keeping food in air tight containers helps to slow down oxidation.
ii) Calcination –It is for carbonate ores.
The ore is heated in limited supply of air.
Roasting - It is for sulphide ores.
The ore is heated in presence of air.
b) It is easier to obtain a metal from its oxide, as compared to its sulphides and carbonates. Therefore, prior to reduction, the metal sulphides and carbonates must be converted into metal oxides.
Calcination is used to reduce carbonate ores.
ZnCO3(s)+heat→ZnO(s)+CO2(g)
The metal oxides are then reduced to the corresponding metals by using suitable reducing agents such as carbon. For example, when zinc oxide is heated with carbon, it is reduced to metallic zinc.
ZnO(s)+C(s)→Zn(s)+CO2(g)
i) CORROSION: - The slow destruction of metals by the action of moisture and air on the metal is called corrosion.
Eg: - rusting of iron, green layer above copper etc.
Prevention of corrosion – Galvanization is a method of protecting steel and iron from rusting by coating them with a thin layer of zinc.
RANCIDITY: - The degradation of fats and oils by getting oxidized or by the action of Oxygen upon them is called rancidity.
Eg: - An unusual smell coming out of chips after their expiry, etc.
Prevention of rancidity- Usually substances which prevent oxidation (antioxidants) are added to foods containing fats and oil. Keeping food in air tight containers helps to slow down oxidation.
ii) Calcination –It is for carbonate ores.
The ore is heated in limited supply of air.
Roasting - It is for sulphide ores.
The ore is heated in presence of air.
b) It is easier to obtain a metal from its oxide, as compared to its sulphides and carbonates. Therefore, prior to reduction, the metal sulphides and carbonates must be converted into metal oxides.
Calcination is used to reduce carbonate ores.
ZnCO3(s)+heat→ZnO(s)+CO2(g)
The metal oxides are then reduced to the corresponding metals by using suitable reducing agents such as carbon. For example, when zinc oxide is heated with carbon, it is reduced to metallic zinc.
ZnO(s)+C(s)→Zn(s)+CO2(g)
