6. (i) A piece of moist blue litmus paper is placed in a gas jar of chlorine.   7. (ii) A piece of moist red litmus paper is placed in a gas jar of ammonia.   8. (iii) Silver nitrate solution is added to dilute hydrochloric acid.   9. (iv) Zinc oxide is heated.   10. (v) A glowing splint is introduced into a gas jar containing oxygen.