A sodium salt X gives with MnO2 and conc. H2SO4 a greenish-yellow gas, a white precipitate with AgNO3 that dissolves in dilute ammonia, and red vapours with K2Cr2O7 and conc. H2SO4. Atomic masses: Na 23, Cl 35.5. The mass of the greenish-yellow gas obtained from 5.85 g of X with excess MnO2 and acid is

JEE Advanced levelSingle correct optionDifficulty 3 of 3qa053

A sodium salt X gives with $MnO X_{2}$ and conc. $H X_{2} SO X_{4}$ a greenish-yellow gas, a white precipitate with $AgNO X_{3}$ that dissolves in dilute ammonia, and red vapours with $K X_{2} Cr X_{2} O X_{7}$ and conc. $H X_{2} SO X_{4}$ . Atomic masses: Na 23, Cl 35.5. The mass of the greenish-yellow gas obtained from 5.85 g of X with excess $MnO X_{2}$ and acid is

The three observations identify X as

NaCl

2 NaCl + MnO X_{2} + 2 H X_{2} SO X_{4} Na X_{2} SO X_{4} + MnSO X_{4} + Cl X_{2} + 2 H X_{2} O

gives 1 mol

Cl X_{2}

per 2 mol NaCl. Moles NaCl = 5.85/58.5 = 0.100, so 0.0500 mol

Cl X_{2}

(M = 71) = 3.55 g. The value 7.10 g assumes 1 mol

Cl X_{2}

per mole NaCl.