Question
Chemistry Question on Organic Chemistry- Some Basic Principles and Techniques
A1 and A2 are two ores of metal M. A1 on calcination gives black precipitate, CO2 and water, and A2 forms a green-coloured complex with acidified K2Cr2O7. 
A1 and A2 respectively are
A
(A) CuCO3.Cu(OH)2 and Cu2S
B
(B) Cu2S and CuCO3.Cu(OH)2
C
(C) CuCO3 and Cu2S
D
(D) CuO and CuCO3
Answer
(A) CuCO3.Cu(OH)2 and Cu2S
Explanation
Solution
Explanation:
A1 will be malachite, i.e.CuCO3⋅Cu(OH)2A2 will be copper glance, i.e. Cu2SThe confirmatory reactions are as follows:(a) For Malachite(i) CuCO3⋅Cu(OH)2− Calanation ⟶2CuUO⏟bladk solid +CO2↑+H2O(ii) CuCO3⋅Cu(OH)2⟶HClCuCl2+CO2↑+H2OCuCl2⟶K()C2l2ppt↓+KCl+I2(b) For Copper Glance cu2S− Roasting O2cu2O+SO2↑Cu2S+Cu2O⟶Cu+SO2↑SO2 is the gas which gives green colour with acidified K2Cr2O73SO2+K2Cr2O7+H2SO4⟶K2SO4+Cr2(SO4)3+4H2O