Which of the following does not involve a chemical reaction?

35 Which of the following are endothermic reactions and which are exothermic reactions ?

(i) Burning of natural gas

(ii) Photosynthesis

(iii) Electrolysis of water

(iv) Respiration

(v) Decomposition of calcium carbonate

36 One of the following does not happen during a chemical reaction. This is: 38 You are given the solution of lead nitrate. In order to obtain a yellow precipitate you should mix with it a solution of: 39 An acid which can decolourise purple coloured potassium permanganate solution is: