Identify the type of reaction in the following and define each of them. (i) Carbohydrates are broken down to form glucose. (ii) Tarnishing of copper. (iii) Heating of ferric oxide with aluminium powder. (iv) Blue colour of copper sulphate solution disappears when zinc dust is added to it. (v) Dilute sulphuric acid is adeed to sodium hydroxide solution .

(i) hydrolysis; (ii) combination;  (iii) single replacement;  

(iv) single replacement; (v) double replacement

Explanation:

(i) Carbohydrates are broken down to form glucose

Carbohydrates must react with water to form glucose.

For example,

C₆H₁₁O₅-O-C₆H₁₁O₆ + H-O-H ⟶ 2C₆H₁₂O₆

       maltose                                          glucose

This is a hydrolysis reaction — the reaction of a compound in which a molecule of water breaks one or more bonds to form new substances.

The reaction is not a decomposition (a reaction in which a compound breaks down into two or more simpler substances), because two different molecules are involved.

(ii) Tarnishing of copper.

Cu + S ⟶ CuS

This is a combination or synthesis reaction — in which two or more substances combine to form a single new substance.

(iii) Heating of ferric oxide with aluminium powder

Fe₂O₃ + 2Al ⟶ Al₂O₃ + 2Fe

This is a single displacement or single replacement reaction — in which one element replaces another element in a compound.

Here, Al is replacing Fe in its oxide.

(iv) Blue colour of copper sulphate solution disappears when zinc dust is added to it

CuSO₄ + Zn ⟶ ZnSO₄  + Cu

This is a single displacement or single replacement reaction.

Here, Zn is replacing Cu in its sulfate.

(v) Dilute sulfuric acid is added to sodium hydroxide solution  

H₂SO₄ + 2NaOH ⟶ Na₂SO₄ + 2H₂O

2H⁺, SO₄²⁻ + 2Na⁺OH⁻ ⟶ 2Na⁺, SO₄²⁻ + 2H-OH

This is a double displacement or double replacement reaction — in which the positive and negative ions of two ionic compounds exchange places to form two new compounds.

The Na⁺ ions are replacing the H⁺ ions in the sulfuric, forming sodium sulfate and water,  

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