The sulphate salt X of a 3d-series element A, on heating, produces a mixture of two gases both containing sulphur. Adding a few drops of HNO3 to a solution of X, followed by KSCN, gives a blood-red colour; excess sodium oxalate removes the red colour by forming complex Y. Which of the foll

Question

The sulphate salt X of a 3d-series element A, on heating, produces a mixture of two gases both containing sulphur. Adding a few drops of HNO3 to a solution of X, followed by KSCN, gives a blood-red colour; excess sodium oxalate removes the red colour by forming complex Y. Which of the following statements are correct? (A) Element A reacts with dilute HCl to form a salt in the +3 oxidation state and releases H2(g). (B) Decomposition of X produces an oxide of A in the +3 oxidation state. (C) The two gases produced are SO2 and SO3. (D) Element A is diamagnetic. (E) Complex Y is paramagnetic.

Accepted Answer

(B) Decomposition of X gives oxide of A in +3 state. A is iron (Fe). X is FeSO4 (ferrous sulphate). Heating: 4FeSO4 -> 2Fe2O3 + 4SO2 + O2, or at higher temperature SO3 also forms; two S-containing gases are SO2 and SO3. HNO3 oxidises Fe²+ to Fe³+; KSCN gives blood red [Fe(SCN)]²+. Excess oxalate forms [Fe(ox)3]³- (Y), displacing SCN-. A: Fe + dil HCl -> FeCl2 (+2 state, NOT +3) -> FALSE. B: Fe2O3 formed (+3 state) -> TRUE. C: SO2 and SO3 -> TRUE. D: Fe is paramagnetic -> FALSE. E: [Fe(ox)3]³- has Fe³+ (d⁵ high-spin, 5 unpaired) -> paramagnetic -> TRUE. Correct statements: B, C, E.

Solution

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