When a magnesium ribbon is heated, it burns in air to form magnesium oxide. Write a balanced chemical equation for this reaction. Name (i) substance oxidised, and (ii) substance reduced.

34 When copper powder is heated strongly in air, it forms copper oxide. Write a balanced chemical equation for this reaction. Name (i) substance oxidised, and (ii) substance reduced. 35 Define the following in terms of gain or loss of hydrogen with one example each:

(i) oxidation (ii) reduction

36 What is meant by

(a) displacement reaction, and

(b) double displacement reaction? Explain with the help of one example each.

37 Why are decomposition reactions called the opposite of combination reactions? Explain with equations of these reactions.