1.

A_1 and A_2 are two ores of metal M.A_1 on calcination gives black precipitate, CO_2 and water. Identify A_1 and A_2.

Answer»

Solution :`A_1` is malachite `CuCO_3.Cu(OH)_3`
`CuCO_3Cu(OH)_2overset(DELTA)toCuO+CO_2uarr+H_2O`
`CuO` is the black solid.
`CuCO_3.Cu(OH)_2overset(dil.HCl)toCuCl_2+CO_2+H_2O`
`CuCl_2overset(KI)toCu_2I_2+KCl+I_2`
`A_2` is COPPER glance `Cu_2S`, a sulphide ore.
`Cu_2Sunderset(Delta)overset(O_2)toCu_2O+SO_2`
`Cu_2S+Cu_2OtoCu+SO_2`
The GAS `SO_2` gives GREEN colour with acidified `K_2Cr_2O_7.K_2Cr_2O_7+H_2SO_4+3SO_4toK_2SO_4+Cr_2(SO_4)_3+4H_2O`


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