Question

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 ?

• A. $67.2\, L$
• B. $44.8\,L$
• C. $22.4\, L$
• D. $89.6 \,L$

Answer 1

Answer: (A)

$67.2\, L$

Answer 2

$2BCl_{3} + 3H_{2} \to 2B + 6HCl$ or $BCl_{3} + \frac{3}{2} H_{2} \to B + 3HCl$ Now, since $10.8 \,gm$ boron requires hydrogen $= \frac{3}{2} \times 22.4 \,L$ at N.T.P hence $21.6 \,gm$ boron requires hydrogen $\frac{3}{2} \times \frac{22.4}{10.8}\times21.6 = 67.2 \,L$ at N.T.P.