NCERT Class X Science Class: Chapter –1. Chemical Reactions and Equations – Part-9

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Question 41:

What happens when a piece of

  1. Zinc metal is added to copper sulphate solution?

  2. Aluminium metal is added to dilute hydrochloric acid?

  3. Silver metal is added to copper sulphate solution?

Also, write the balanced chemical equation if the reaction occurs

Answer:

  1. Zinc being more reactive than copper displaces copper from its solution and a solution of zinc sulphate is obtained

    This is an example of displacement reaction

  2. Aluminium being more reactive displaces hydrogen from dilute hydro chloric acid solution and hydrogen gas is evolved.

  3. Silver metal being less reactive than copper cannot displace copper from its salt solution. Therefore, no reaction occurs

Question 42:

What happens when zinc granules are treated with dilute solution of , also write the chemical equations if reaction occurs.

Answer:

  1. Displacement reaction has taken place coz Zn is more reactive than hydrogen

  2. Displacement reaction has taken place

  3. Zinc reacts with dilute Nitric acid to produce Zinc nitrate, nitric oxide and water

    Zinc reacts with concentrated Nitric acid to produce Zinc nitrate, nitrogen dioxide and water.

  4. no reaction take place coz sodium is more reactive than zinc

Question 43:

On adding a drop of barium chloride solution to an aqueous solution of sodium sulphite, white precipitate is obtained.

  1. Write a balanced chemical equation of the reaction involved

  2. What other name can be given to this precipitation reaction?

  3. On adding dilute hydrochloric acid to the reaction mixture, white precipitate disappears. Why?

Answer:

  1. On adding a drop of Barium Chloride solution to an aqueous solution of sodium sulphite, white precipitate is obtained. This white precipitate is a barium sulphite.

    Balanced chemical equation:

  2. This reaction is also known as double displacement reaction

  3. is a salt of a weak acid therefore dilute acid such as decomposes barium sulphate to produce Sulphur dioxide gas which has the smell of burning sulphur.

is soluble in water, hence white precipitate disappears