CBSE Class 10 Science 2023: question 27

Hints

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Step-by-step solution

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1. (a) A double displacement reaction is one in which the reactants exchange ions with each other to form new compounds.

   1 mark

2. (b)(i) Neutralisation: $\mathrm{HCl}(\mathrm{aq})+\mathrm{NaOH}(\mathrm{aq})\to \mathrm{NaCl}(\mathrm{aq})+{\mathrm{H}}_2\mathrm{O}(\mathrm{l})$

   ½ mark

3. Justification: an acid reacts with a base to give a salt and water. The ${\mathrm{H}}^{+}$ and $\mathrm{N}{\mathrm{a}}^{+}$ ions exchange partners, so it is also a double displacement.

   ½ mark

4. (ii) Precipitation: $\mathrm{N}{\mathrm{a}}_2\mathrm{S}{\mathrm{O}}_4(\mathrm{aq})+\mathrm{BaC}{\mathrm{l}}_2(\mathrm{aq})\to \mathrm{BaS}{\mathrm{O}}_4(\mathrm{s})+2NaCl(\mathrm{aq})$

   ½ mark

5. Justification: the ions are exchanged and an insoluble white precipitate of $\mathrm{BaS}{\mathrm{O}}_4$ is formed.

   ½ mark

Answer: (a) Reaction with exchange of ions between reactants; (b)(i) HCl + NaOH → NaCl + H₂O; (ii) Na₂SO₄ + BaCl₂ → BaSO₄↓ + 2NaCl

Revise the chapter

• Chapter: Chemical Reactions and Equations (notes, formulas, where marks are lost and every past question)