Hydrochloric Acid⚡️

This is the most commonly used acid in I/GCSE Chemistry.

• The stomach produces hydrochloric acid(HCL) to help with digestion. The enzymes in the stomach work best in an acidic environment.
• Having acid in the stomach helps to kill bacteria- reducing risk of food poisoning.
• Indigestion is caused by too much hydrochloric acid in the stomach. Indigestion tablets contain bases such as calcium carbonate, which neutralise the excess acid.

Reactions of Acids💥

Metal oxides and metal hydroxides are often bases, this means they can be neutralised with acids to form a salt and water.

• acid+metal hydroxide reacts to form salt+water
• acid+metal oxide reacts to form salt+water

The combination of metal and acid decide the salt.

• Hydrochloric acid+ copper oxide reacts to form copper chloride +water
• Sulfuric acid+ zinc hydroxide reacts to form zinc sulfate + water
• Nitric acid + potassium hydroxide reacts to form potassium nitrate + water

Metal carbonates give salt+water+carbon dioxide

• e.g. sulfuric acid+ copper carbonate reacts to form copper sulfate+ water+ carbon dioxide

Electrolysis

Electrolysis is the breaking down of (decomposition) of a compound using electrical energy. The electricity comes from a d.c. direct current.

• Liquid to conduct electricity this is called the electrolyte.
• The electricity is applied to the electrolyte by two electrodes.
• The electrolyte contains the compound, which is broken down into its component parts.
• The component parts are released as atoms or molecules- often a a gas.

You can test for Chlorine and Hydrogen Gases

• Chlorine; Chlorine bleaches damp blue litmus paper, turning it white. It may turn red for a moment because a solution of chlorine is acidic.
• Hydrogen:Hydrogen makes a pop with a lighted splint. This is because the hydrogen burns with the oxygen in the air to form H2O.

The electrolysis of salt produces chlorine.

• Sea water can be decomposed by electrolysis. This is a useful way to make chlorine gas. Chlorine gas is toxic so the manufacture of it a hazardous process.
• Chlorine has three main uses: to treat water supplies- it kills bacteria and other microorganisms so that the water is safe to drink, manufacture of bleach, its used to make the polymer poly(chloroethene)-PVC.
• Electrolysis of water produces hydrogen and oxygen gas. You can test for oxygen by checking if the gas relights a glowing splint.

Reference: https://www.savemyexams.co.uk/notes/a-level-chemistry-cie-until-2021/5-physical-chemistry-pre/5-3-electrochemistry-pre/5-3-2-electrolysis-pre/

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Drafted by Catrina (Chemistry)