A white salt X gives a brick-red flame. Its aqueous solution gives a white curdy precipitate with $AgNO X_{3}$ that dissolves in dilute ammonia, and a white precipitate with ammonium oxalate. Heated with solid $K X_{2} Cr X_{2} O X_{7}$ and concentrated $H X_{2} SO X_{4}$ , X gives orange-red vapours. Identify X and the maximum moles of $CrO X_{2} Cl X_{2}$ obtainable from $1.0 mol$ of X with excess reagents.

Answer: B

The brick-red flame and oxalate precipitate show

Ca X^{2 +}

; the curdy precipitate soluble in ammonia and the chromyl test show chloride, so X is

CaCl X_{2}

. From

K X_{2} Cr X_{2} O X_{7} + 4 NaCl + 6 H X_{2} SO X_{4} 2 CrO X_{2} Cl X_{2} + \dots

, 2 Cl give 1

CrO X_{2} Cl X_{2}

; each

CaCl X_{2}

has 2 Cl, so 1.0 mol gives 1.0 mol.