Chemistry-Acids and Bases

Acids	Bases
Have a sour taste	Have a bitter taste and a soapy feel
Turns blue litmus paper red	Turns red litmus paper blue
Dissolve in water to form solutions which conduct electricity	Produce ammonia gas when heated with ammonium salts
React with reactive metals to form hydrogen and a salt. The general equation for the reaction is: Metal + acid → salt + hydrogen	Reacts with a solution of one metal salt to give metal hydroxide and another metal salt
pH less than 7
Hydrogen ions must be present (H+)

Concentration and strength
1. Concentration tells us how much a substance is dissolved in 1 cm3 of the solution.
2. Strength refers to how easily an acid or an alkali dissociates when dissolved in water.

The pH scale
1. The pH scale is used to determine if a given substance is acid, alkaline or neutral.
2. The pH of colourless solutions can be determined using the Universal indicator.
3. It is important to control the pH of soil. Most plants grow best when the pH is around 7.
4. Quicklime (calcium oxide) and slaked lime (calcium hydroxide) are commonly used to reduce the acidity of soil.

Universal indicator
pH value can be determined using the universal indicator. It gives different colours in solutions of different pH.
*The more hydrogen ions there are, the lower the pH value, the stronger the acid.
pH can be used to compare strengths of acids and alkalis of the same concentration.

Types of oxide
1. Metals react with oxygen to form basic oxides or amphoteric oxides.
2. Non-metals react with oxygen to form acidic oxides or neutral oxides.
3. Basic oxides that are soluble in water are called alkalis.
4. Basic oxides that are insoluble in water are called insolubles bases.

Sulphuric dioxide and sulphuric acid
1. Sulfur dioxide is used
-for manufacturing sulphuric acid
-as a bleaching agent
-as a food preservative

2. Sulphuric acid is used
-for manufacturing fertilisers
-for manufacturing detergents
-in car batteries