JEE PYQ: Ionic Equilibrium Question 10
Question 10 - 2020 (02 Sep Shift 1)
Type: MCQ
For the following Assertion and Reason, the correct option is:
Assertion (A): When Cu(II) and sulphide ions are mixed, they react together extremely quickly to give a solid.
Reason (R): The equilibrium constant of $\text{Cu}^{2+}(aq) + \text{S}^{2-}(aq) \rightleftharpoons \text{CuS}(s)$ is high because the solubility product is low.
(a) (A) is false and (R) is true
(b) Both (A) and (R) are false
(c) Both (A) and (R) are true but (R) is not the explanation for (A)
(d) Both (A) and (R) are true and (R) is the explanation for (A)
Show Answer
Answer: (c)
Solution
Cesium has lowest ionisation enthalpy and hence it shows photoelectric effect to the maximum extent. So, it is used in photo electric cell. CuS has very low $K_{sp}$, so the equilibrium constant for precipitation is very high, making the reaction very fast.
BETA
