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Dear student, Following experiment will prove that hydrochloric acid contain hydrogen and chlorine. Take a voltameter used for electrolysis of water fitted with the platinum cathode and a graphite anode. Pour 4 molar HCI into the voltmeter and pass direct current through it. A colorless gas is evolved at the cathode and a greenish gas is evolved at the anode. When a burning splinter is brought near a colorless gas, it bursts into a flame thereby proving that it is hydrogen gas. When moist starch iodide paper is held in the greenish-yellow gas. it turns blue-black. thereby proving that the gas is chlorine. 2HCl→ H2 + Cl2 ​Hence proved that hydrochloric acid contains both hydrogen and chlorine. Regards,