Acids

Acids

1. Acid in your stomach

   • Your stomach contains hydrochloric acid (HCI).
     • It used to: Kill germs; Help break down food by making the enzymes work properly (They need acidic conditions)
       • Too much acid in your stomach causes indigestion/heartburn. Medicenes antacids can neutralise excess stomach acid. Antacid contain bases.
         • The redder the solution means more acidic, if it goes purple it has more alkaline.

2. Litmus Indicator

   • Paper or liquid: Red litmus paper goes blue in alkali and Blue litmus paper goes red in acid.

3. Hazard Symbols

   • Oxidising produces oxygen which allows other materials to burn more fiercely. Examples: Liquid Oxygen
     • Highly Flammable means catches fire easily, example: Petrol
       • Toxic can cause death either by swallowing, breathing in or absorption through the skin. Examples: Hydrogen cyanide.
         • Harmful is like toxic but not quite as dangerous. Examples are Copper Sulfate.
           • Irritant isn't corrosive but can cause reddening/blistering of the skin. Examples are Bleach, children, ect.
             • Corrosive attacks and destroys the living tissues, including eyes and skin. Examples are: Concentrated sulfuric acid.

4. Neutralisation reactions between acids and bases make salts.

   • An acid and a base react together to form salt and water. The products of the reaction aren't strongly acidic/alkaline- they're neutral. So it's called a "Neutralisation reaction". N reactions can be used to make salts, which have a bunch of exciting uses. 1) Salts are used in fertilisers- e.g ammonium nitrate, ammonium phosphate. 2) Salts are used in fireworks as colouring agents-e.g. Calcium chloride (for an orange colour), copper chloride (for a bluey-green colour)

5. Reactions of Acids

   • Metal oxides and Metal Hydroxides are generally bases. This means they can be neutralised with acids to form a salt and water.
     • Acid+metal oxide=salt+water
     • Acid+metal hydroxide=salt+water
     • To get the hang of it...
       • HydroCHLORIC acid+COPPER oxide= Copper chloride + water
         • SULFURIC acid + ZINC oxide= Zinc sulfate+water

6. Metal Carbonates give Salt+Water+Carbon Dioxide

   • Acid + Metal Carbonate = Salt + Water + Carbon Dioxide
     • CARBONates give off CARBON dioxide when they Neutralise acids.
       • An Example: HydroCHLORIC acid + SODIUM CARBONATE + SODIUM CHLORIDE + water + carbon dioxide

7. Electrolysis

   • It means splitting up the electricity.
   • Electrolysis is the breaking down (decomposition) of a compound using electrical energy. The electricity comes from a D.C (Direct current) source. It requires liquid to conduct the electricity, called the electrolyte. Electricity is applied to the elelectrolyte by 2 electrodes. Electrode contains the compound, which is broken down into its component parts. The component parts are released as atoms/molecules-often as a gas.
   • Chlorine: Chlorine bleaches damp litmus paper, turning it white. (It may turn red for a moment first though- thats because the solution of chlorine is acidic). Hydrogen: Hydrogen makes a "squeaky pop" with a lighted splint. (The noise comes from the hydrogen burning with the oxygen in the air to for H20)
   • Electrolysis of water gives Hydrogen and Oxygen
     • 1) Sea water or brine (sodium chloride solution) can be decomposed by electrolysis.
       • 2) This is really handy to make chlorine gas.
         • 3) Chlorine gas is toxic- so this makes the manufacture of it a hazardous process.
           • 4) You need to know about 3 uses of chlorine: (1) It's used to treat water supplies-it kills bacteria and other micro-organisms so that water's safe to drink. (2) It's needed for the manufacture of bleach. (3) Its used to make polymer poly(chloroethene)-PVC.
             • Water can be decomposed by electrolysis to give 2 useful products: a) Hydrogen Gas b) Oxygen Gas
               • You can test for oxygen by checking if the gas relights a glowing splint.

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