Chemical Properties of Acid
These notes are based on the chapter Acids Bases and Salts from NCERT book based on CBSE syllabus.
- Types of acid
- Reaction of acid with metal
What is acid?
Acid is a substance which has sour taste and which turns blue litmus paper to red. If a substance tastes sour then it must contain acid. Curd, tamarind, lemon, etc. tase sour because they contain acid. If a substance does not contain acid, it does not taste sour.
Types of Acids
What are different types of acid?
Acids are divided into two types on the basis of their occurrence, viz. Natural acids and Mineral acids.
- Natural Acid: Acids which are obtained from natural sources are called natural acid. These acids are also called organic acid because they comes from living beings. Examples: vinegar, citric acid, tartaric acid, etc.
- Mineral Acids: Acids which are prepared from mineral are known as mineral acids. They are also called inorganic acids, man-made acids or synthetic acid. Examples: hydrochloric acid, sulphuric acid, nitric acid, etc.
Organic acids and their sources
- Acetic acid: Vinegar
- Ascorbic acid: Guava, amla
- Citric acid: Lemon, orange and other citrus fruits
- Lactic acid: Sour milk, curd
- Methanoic acid: Ant sting, nettle sting
- Oxalic acid: Tomato
- Tartaric acid: Tamarind
Reaction of acids with metal
What happens when an acid reacts with metals? Acids give hydrogen gas along with respective salt when they react with a metal.
Metal + Acid ⇨ Salt + Hydrogen
Example 1
Hydrogen gas and zinc chloride are formed when hydrochloric acid reacts with zinc metal.
Zn + 2HCl ⇨ ZnCl2 + H2
Example 2
Hydrogen gas and sodium chloride are formed when hydrochloric acid reacts with sodium metal.
2Na + 2HCl ⇨ 2NaCl + H2
Example 3
Hydrogen gas and iron chloride are formed when hydrochloric acid reacts with iron.
Fe + 2HCl ⇨ FeCl2 + H2
Example 4
Hydrogen gas and zinc sulphate are formed when zinc metal reacts with sulphuric acid
Zn + H2SO4 ⇨ ZnSO4 + H2
Test for hydrogen gas: The gas evolved after reaction of acid with metal can be tested by bringing a burning candle near it. If the candle burns with pop sound, then it confirms the evolution of hydrogen gas. This is the characteristic test for hydrogen gas.
Reaction of Metal with Nitric Acid
What happens when a metal reacts with nitric acid? When a metal reacts with nitric acid then hydrogen gas is not formed. It happens because of following reason.
Nitric acid is a strong oxidising agent. Nitric acid oxidises H2 to make water. In the reaction with metal, nitric acid itself gets reduced to oxides of nitrogen such as NO2 or NO or N2O
Reaction between nitric acid and copper
In this reaction of nitric acid with copper, nitrogen oxide, water and copper nitrate are formed. Hydrogen gas is not formed in this reaction.
3Cu + 8HNO3 → 3Cu(NO3)3 + 2NO + 4H2O
But magnesium and manganese react with very dilute nitric acid (HNO3 to produce H2 gas.
Reaction between nitric acid and magnesium
In this reaction of nitric acid with magnesium, hydrogen gas and magnesium nitrate are formed.
Mg + 2HNO3 → Mg(NO3)2 + H2
Reaction between nitric acid and manganese
In this reaction of nitric acid with manganese, hydrogen gas and manganee nitrate are formed.
Mn + 2HNO3 → Mn(NO3)2 + H2
Reaction between nitric acid and zinc
In this reaction of nitric acid with zinc, hydrogen gas and zinc nitrate are formed.
Zn + 2HNO3 → Zn(NO3)2 + H2
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