Question

The correct option(s) to distinguish nitrate salts of $Mn^{2 +}$ and $Cu^{2 +}$ taken separately is (are)

(1) $Mn^{2 +}$ shows the characteristic green colour in the flame test

(2) only $Cu^{2 +}$ shows the formation of precipitate by passing $H_{2}S$ in acidic medium

(3) only $Mn^{2 +}$ shows the formation of precipitate by passing $H_{2}S$ in faintly basic medium

(4) $\text{Cu}^{2 +} \left|\right. \text{Cu}$ has higher reduction potential than $\text{Mn}^{2 +} \left|\right. \text{Mn}$ (measured under similar conditions)

• A. 1, 2
• B. 1, 3
• C. 2, 4
• D. 1, 2, 4

Answer 1

Answer: (C)

$\left(A\right)$ Manganese show pale purple colour in flame test.

$\left(B\right) \, $ $Cu^{2 +}\overset{ H_{2} S H C l }{ \rightarrow }\underset{\text{Black ppt.}}{C u S \downarrow}$

$\left(C\right)$ Both $Cu^{2 +}$ and $Mn^{2 +}$ form precipitate with $H_{2}S$ in basic medium.

$\left(\text{D}\right) \text{E}_{\left(\text{Cu}\right)^{2 +} \left|\right. \text{Cu}}^{\text{o}} = + 0.34 \text{V} , \text{E}_{\left(\text{Mn}\right)^{2 +} \left|\right. \text{Mn}}^{\text{o}} = - 1.18 \text{V}$