JEE Advanced levelSingle correct optionDifficulty 3 of 3ph220
1.0 mol of Xe reacts completely with 1.6 mol of FX2 to give only XeFX2 and XeFX4 (all Xe and all FX2 used up). Molar masses: Xe 131, F 19, so XeFX4 = 207 gmol−1. The mass of XeFX4 formed is
A82.8g
B62.1g
C165.6g
D124.2g
Answer: D
Let a mol XeFX2 and b mol XeFX4 form. Xe balance: a+b=1.0; FX2 balance: a+2b=1.6. Subtracting gives b=0.60 and a=0.40. Mass of XeFX4=0.60×207=124.2g.