Question

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

• A. 89.6 L
• B. 67.2 L
• C. 44.8 L
• D. 22.4 L

Answer 1

Answer: (B)

67.2 L

Answer 2

(2)

2BCl3 + 3H2 $\longrightarrow$2B + 6HCl

2 mol 3 mol 2 mol

21.6 g B = 2 mol B = 3 mol H2

PV =nRT

$\therefore V = \frac{nRT}{P} = \frac{3 \times 0.0821 \times 273}{1} = 67.2L$