Qualitative Analysis - Result Question 48
####51. $A _1$ and $A _2$ are two ores of metal $M . A _1$ on calcination gives black precipitate, $CO _2$ and water.
$$ A _2 \xrightarrow{\text { Roasting }} \text { Metal }+\underset{\substack{\text { Gas } \\ \text { Green colour }}}{K _2 Cr _2 O _7+H _2 SO _4} $$
Identify $A _1$ and $A _2$.
(2004)
Show Answer
Solution:
- $A _1=Cu(OH) _2 \cdot CuCO _3$ and $A _2=Cu _2 S$
$$ \begin{aligned} A _1 \xrightarrow{\text { Calcination }} 2 CuO+CO _2+H _2 O \\ \text { Black } \\ A _1 \xrightarrow{\text { Dil. } HCl} CuCl _2+CO _2+H _2 O \\ 2 CuCl _2+4 KI \longrightarrow 2 CuI+I _2+4 KCl \\ 2 Cu _2 S\left(A _2\right)+3 O _2 \longrightarrow 2 Cu _2 O+2 SO _2 \\ Cu _2 S+2 Cu _2 O \stackrel{\Delta}{\longrightarrow} 6 Cu+SO _2 \end{aligned} $$
