Question

If $\mathop {CuI}\nolimits_2 :Brown::AgCl:$

Answer 1

To deal with this question we should know about the precipitation reaction. When the two ionic liquid solutions react, we get a precipitate of insoluble salt in aqueous solution.

Complete step by step answer:
(a) Precipitation reaction: It is a kind of chemical reaction in which two soluble salts in a fluid solution mixes and one of the items is an insoluble salt called a precipitate. Precipitation reactions can help to determine the presence of various ions in solution. A precipitation reaction can occur when two solutions containing different salts are mixed, and a cation/anion pair in the resulting combined solution forms a soluble salt; this salt then precipitates out of the solution. To know whether a precipitation reaction occurs or not we will use solubility rules for common ionic solids .Sometimes the formation of a precipitate indicates the occurrence of a chemical reaction.
(b) To deal with the question we should write the precipitation reaction of aqueous silver nitrate when added to the solution containing potassium chloride $\left( {KCl} \right)$.
$\mathop {AgNO}\nolimits_3 \left( {aq} \right) + KCl\left( {aq} \right) \to AgCl\left( s \right) + \mathop {KNO}\nolimits_3 \left( {aq} \right)$
Here silver chloride is the precipitate and is white in colour.
Moreover in case of $CuI$ precipitate appears to be brown in colour because the iodine is sparingly soluble in water. The iodide ion is sufficiently strong reducing agent so that it reduces the $Cu\left( {II} \right)$to$Cu\left( I \right)$

So, $\mathop {CuI}\nolimits_2 : Brown :: AgCl : White$.

Note:
copper iodide will have a redox reaction whereas silver chloride undergoes a precipitation reaction and students get confused between redox reaction and precipitation reaction.