Chemistry

For Summer Exams 2012

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  • Created by: Laura
  • Created on: 03-06-12 20:12

The pH Scale

The pH scale is used to show how acidic or alkaline a substance is. It runs from 0 (being highly acidic) 7 which is neutral and to 14 (being highly alkaline).

Indicators are used to show whether a solution is acidic, alkaline or neutral by the way their colours change. Some common indicators are: Universal Indicator, Litmus Paper

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Acids and Bases

A base is a substance that neutralises an acid. An alkali is a soluble base. (All alkalis are bases, but not all bases are alkalis)

 An acid reacts with an alkali to produce a salt and water. This type of reaction is called a neutralisation reaction.

Metal oxides dissolve to form alkaline solutions.

Non-metal oxides dissolve to form acidic solutions.

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Reactions

1. Acid + Base Salt + Water

2. Acid + Carbonate Salt + Water + Carbon Dioxide

3. Acid + Metal Salt + Hydrogen

N.B. Metals below hydrogen in the reactivity series (copper, silver, gold) will not react with acids.

· Reactions involving hydrochloric acid produce chlorides.

· Reactions involving sulphuric acid produce sulphates.

· Reactions involving nitric acid produce nitrates.

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pH Examples

1.Hydrochloric Acid                       11. Ammonia

2.Lemon Juice                               12. Soapy Water

3.Orange Juice                              13. Bleach

4. Acid Rain                                   14. Drain Cleaner

5. Black Coffee

6. Saliva

7. Pure Water

8. Sea Water

9.  Baking Soda

10. Milk

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