Question

(a) What happens when methane (natural gas) burns in air? Write the chemical equation of the reaction involved.
(b) What happens when ethanoic acid reacts with sodium carbonate? Write chemical equation of the reaction involved.
(c) Give a test that can be used to differentiate chemically between butter and cooking oil.

Answer 1

a) When methane (natural gas) burns in air, carbon dioxide and water vapour are formed along with the release of a large amount of heat. This process is known as combustion.

The chemical equation of the combustion reaction is as follows:
CH₄ + 2O₂ → CO₂ + 2H₂O + Heat + Light

(b) When ethanoic acid reacts with sodium carbonate, a brisk effervescence of carbon dioxide gas is observed. The salt formed due to this reaction is sodium ethanoate.

The chemical equation for the above reaction is as follows:
2CH₃COOH + Na₂CO₃ → 2CH₃COONa + CO₂ + H₂O

(c) Bromine water test can be used to chemically differentiate between a butter and cooking oil.
Take two test tubes, one with a small amount of butter in it and the other with some cooking oil.
Add bromine water to both the test tubes.
Observation:
(i) Cooking oil decolourises bromine water indicating that it is an unsaturated compound.
(ii) Butter does not decolourise bromine water indicating that it is a saturated compound.