What volume of hydrogen gas, at 273 K and 1 atm

• Stoichiometry

What volume of hydrogen gas, at 273 K and 1 atm. pressure will be consumed in obtaining 21.6 g of elemental boron (atomic mass = 10.8) from the reduction of boron trichloride by hydrogen?

1. 89.6 L
2. 67.2 L
3. 44.8 L
4. 22.4 L

Answer

2BCl₃ + 3H₂ → 6HCl + 2B

or BCl₃ +  3/2H₂ → 3HCl + B

10.8 g boron requires hydrogen = 3/2 22.4 L

21.6 g boron will require hydrogen

= 3x22.4/(2x10.8) = 67.2 L

The correct option is B.