Chemistry - Acid, Bases and Salts

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Acid:

- 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.

Characteristics:

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

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

Bases:
- 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 

Alkali:
- 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

Properties:
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.
uses:
1. As a bleach
2. Manufacture of wood pulp for paper
3. As a good preservative by killing

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