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Q1. From the following list of substances, choose the substances which meet the description given in parts (i) to (v) below : Ammonium chloride, ammonium nitrate, chlorine, dilute hydrochloric acid, iron, lead nitrate, manganese (IV) oxide, silver nitrate, sodium nitrate, sodium nitrite, sulphur i. Two compounds heated together in solution to produce nitrogen. ii. An element which exists in two crystalline forms. iii. A compound which on heating gives oxygen as the only gaseous product. iv. A substance containing both molecules and ions. v. Two compounds whose aqueous solution give white precipitates with dilute Hydrochloric acid. Q2. What do you see when: i. Sodium hydroxide solution is added to zinc sulphate solution till it is in excess. ii. Chlorine water is exposed to sunlight. iii. Ammonia gas is bubbled through red litmus solution. iv. Barium chloride solution is added to dilute sulphuric acid. Q3. Explain why the following statements are not correct: i. The element nitrogen can be obtained in the pure state by removing carbon dioxide and oxygen from air. ii. Ammonium salts will, on heating, decompose to give ammonia. iii. Lead chloride can be prepared by adding dilute hydrochloric acid to lead sulphate solution iv. 1 gram of any gas occupies 22.4 liters at S.T.P. Q4. i. A solution has a pH of 7. Explain how you would: 1. Increase its pH; 2. Decrease its pH. ii. If a solution changes the color of litmus from red to blue, what can you say? About its pH iii. What can you say about the pH of a solution that liberates carbon dioxide from Sodium carbonate?
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