Calcium carbide containing 20 percent inert impurity by mass (10.0 g sample) reacts completely with water to form ethyne: CaC2 + 2H2O -> C2H2 + Ca(OH)2. If only 75 percent of the ethyne expected is actually collected, find the volume of ethyne at STP in litres, to two decimals. Use molar volume 22.4 L/mol and atomic masses Ca 40, C 12.

JEE Main levelNumerical answerDifficulty 2 of 3hc087

Calcium carbide containing 20 percent inert impurity by mass (10.0 g sample) reacts completely with water to form ethyne: $CaC X_{2} + 2 H X_{2} O C X_{2} H X_{2} + Ca (OH) X_{2}$ . If only 75 percent of the ethyne expected is actually collected, find the volume of ethyne at STP in litres, to two decimals. Use molar volume 22.4 L/mol and atomic masses Ca 40, C 12.

Numerical answer type, answer in L, tolerance 0.05.

Pure

CaC X_{2}

10.0 \times 0.80 = 8.0

g, and its molar mass is 64 g/mol, so it is

0.125

mol. One mole of carbide gives one mole of ethyne, so the theoretical amount is

0.125

mol. The collected amount is

0.125 \times 0.75 = 0.09375

mol, and the volume is

0.09375 \times 22.4 = 2.10