Question

Iodine is formed when potassium iodide reacts with a solution of:
A.$ZnS{O_4}$
B.$CuS{O_4}$
C.${(N{H_4})_2}S{O_4}$
D.$N{a_2}S{O_4}$

Answer 1

Hint: At first think about the products formed when potassium iodide is reacted with zinc sulphate, copper sulphate, ammonium sulphate and sodium sulphate. Among the four compounds the highest possible reaction forms iodine.

Complete step by step answer:
Iodine is formed when potassium iodine reacts with a solution of copper sulphate. The overall reaction is,
$
  CuS{O_4} + 2KI \to Cu{I_2} + {K_2}S{O_4} \\
  2Cu{I_2} \to 2CuI + {I_2} \\
 $
$2CuS{O_4} + 4KI \to C{u_2}{I_2} + {I_2} + 2{K_2}S{O_4}$

So the answer is B.

Additional Information:- Iodine is the heaviest of the stable halogens. It exists as a lustrous, purple-black non-metallic solid at standard conditions that melts to form a deep violet liquid. Iodine exists in many oxidation states. It is the least abundant of stable halogens. Iodine and its compounds are primarily used in nutrition. Iodine is also used as a catalyst in the industrial production of acetic acid and some polymers.
Potassium iodide is a chemical compound, medication and dietary supplement. As a medication it is used to treat hypothyroidism. As a supplement it is used in those who have low intake of iodine in the diet.
Copper sulphate is produced industrially by treating copper metal with hot concentrated sulphuric acid or its oxides with dilute sulphuric acid. Copper sulphate pentahydrate decomposes before melting. It is used to demonstrate the principle of mineral hydration. It is used as electrolyte for galvanic cells, usually as a cathode solution.

Note:
An aqueous solution of copper sulphate is often used as the resistive element in liquid resistors. Copper sulphate directly doesn't give iodine in reaction with potassium iodide. At first it forms copper iodide and then the copper iodide gives iodine.