Analytical Chemistry Question 4
Question: A white crystalline substance dissolves in water. On passing $ H_2S $ in this solution, a black precipitate is obtained. The black precipitate dissolves completely in hot $ HNO_3 $ . On adding a few drops of conc. $ H_2SO_4 $ a white precipitate is obtained. This precipitate is that of
[CPMT 1990]
Options:
A) $ BaSO_4 $
B) $ SrSO_4 $
C) $ PbSO_4 $
D) $ CdSO_4 $
Show Answer
Answer:
Correct Answer: C
Solution:
$ P{b^{+2}}\ +\ H_2S\ \xrightarrow[acidic]{}\ \underset{\text{(Black ppt}\text{.)}}{\mathop{PbS\downarrow \ }}+\ H_2\uparrow $
$ 3PbS+8HNO_3\to 3Pb{{(NO_3)}_2}+2NO+3S $
$ +4H_2O $
$ Pb{{(NO_3)}_2}\ +\ H_2SO_4\ \to \underset{\text{(white ppt}\text{.)}}{\mathop{\ PbSO_4}}\downarrow \ +\ 2HNO_3\uparrow $
BETA
