According to experiment 5, X is a carbonate because it is completely dissolved in HCl and it releases a gas. The cation is a transition metal, because it can change oxidation states easily (that's why Cl2
is used). The metal chloride is volatile (Z).
According to experiment 4, another metal chloride is produced (the oxidation state of the metal is lower now that in Z). Then it can be written:
M=27.9x, for x=2, M=55.8g/mol which would fit for iron. X is FeCO3
, Z is a chloride of iron where iron's oxidation state is bigger than in FeCl2
, so it is FeCl3
is released in experiment 5 and 4, so it should be Y.