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Science · 2024 · 2 marks
CBSE 2024 · Region 2 · Set 1 · Q21
(a) "No precipitation reaction can occur without exchange of ions between the two reactants." Justify this statement giving a balanced chemical…
(a)
"No precipitation reaction can occur without exchange of ions between the two reactants." Justify this statement giving a balanced chemical equation for the reaction.
OR
(b)
Giving one example of each, differentiate between a displacement reaction and a double displacement reaction.
Marking-scheme solution
Exchange of ions can take place only in a double displacement(precipitation) reaction where one of the products gets precipitated.
Reaction:
\(\displaystyle \mathrm{Na}_{2} \mathrm{SO}_{4}(\mathrm{aq})+\mathrm{BaCl}_{2}(\mathrm{aq}) \rightarrow \mathrm{BaSO}_{4}(\mathrm{~s})+2 \mathrm{NaCl}(\mathrm{aq})\) (precipitate)
| Displacement reaction: | Double displacement reaction |
| More reactive metal displaces a less reactive metal. / No exchange of ions takes place. \[ \mathrm{CuSO}_{4}+\mathrm{Fe} \longrightarrow \mathrm{FeSO}_{4}+\mathrm{Cu} \] | an exchange of ions between the reactants takes place. |
| \(\displaystyle \mathrm{Na}_{2} \mathrm{SO}_{4}+\mathrm{BaCl}_{2} \rightarrow \mathrm{BaSO}_{4}+\) $\displaystyle 2$ NaCl |
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