Chemistry - Acid, Bases and Salts

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- Acids are substances that release hydrogen ions (H+) when dissolved in water.

Strength of acid:
- A strong acid ionises fuly in water to produce hydrogen
- A weak acid ionises partially to give hydrogen ions. Most of its molecules remain un-ionised in water.


1. Sour taste
2. Able to conduct electricity
3. Corrosive if concentrated
4. Turn blue litmus paper red

In the reactivity series, only copper and silver cannot react with acid

1. Acid + metal ---> salt + hydrogen
2. Acid + metal carbonate ---> salt + carbondioxide + water
3. Acid + alkali/base ---> salt + water

- Bases are metal oxides that react with acids to produce salts and water.
- Most bases are insoluble except bases with group 1 metals and ammoniumm ion.

In another words, alkali = group 1 metals and ammonium ion 

- When a base dissolves in water, it forms metal hydroxide called an Alkali.

Alkali are substances that release hydroxide ions ((OH-)) when dissolved in water.

- A strong alkali ionises fully in water to produce hydroxide ions
- A weak alkali ionises partially in water to give hydroxide ions

1. Soapy feeling
2. Conductor of electricity
3. Corrosive if concentrated
4. Turn red litmus blue

Ammonia(transfer if needed): 

 Damp red litmus paer is used to test for ammonia gas as it is an alkaline gas. It will change to blue.

Base/alkali + ammonium salt --> salt + ammonia + water

Controlling pH in soils:
- Calcium hydroxide (slaked lime) is used to treat the excess acidity in soils as it
is able to react quickly with acids.
- If the soil is acidic, it affects the growth of healthy plants. Thus, it is important to control the pH in soils.
- Calcium carbonate (limestone) and calcium oxide(lime) can neutralise the acids too but they are slower and less effective.  

Sulfur dioxide:
- Sulfur dioxide is an acidic oxide, and has acidic properties when dissolved in water.
1. As a bleach
2. Manufacture of wood pulp for paper
3. As a good preservative by killing


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