Chemistry
With the help of balanced equations - show how precipitation reactions are used for identifying the positive radicals in three different salts, each having a different cation [positive ion].
Answer
Precipitation reactions are used in analytical chemistry for identifying the positive radical in a salt by analysing the colour of the precipitate.
(i) FeSO4 + 2NaOH ⟶ Na2SO4 + Fe(OH)2 ↓
Identified ion: Fe2+; a dirty green precipitate of iron [II] hydroxide is obtained. Hence, it can be identified.
(ii) CuSO4 + 2NaOH ⟶ Na2SO4 + Cu(OH)2 ↓
Identified ion: Cu2+; a pale blue precipitate of copper [II] hydroxide is obtained. Hence, it can be identified.
(iii) Pb(NO3)2 + 2NaOH ⟶ 2NaNO3 + Pb(OH)2 ↓
Identified ion: Pb2+; a chalky white precipitate of lead [II] hydroxide is obtained. Hence, it can be identified.
Related Questions
Define a displacement reaction with example. State why Zn displaces H2 from dil. H2SO4 but Cu does not.
Explain the term double decomposition precipitation reaction. Give a balanced equation for the preparation of two different insoluble lead salts from their salt solutions by double decomposition precipitation.
Define the term – double decomposition – neutralization reaction with a suitable representation.
Convert :
(a) an insoluble base (b) a soluble base
to their respective soluble salts by neutralization reaction.
Explain the term energy changes in a chemical change. Give an example with a balanced equation, for each of the following reactions:
(a) exothermic reaction
(b) endothermic reaction
(c) photochemical reaction
(d) electrochemical reaction.