Question

The drain cleaner, Drainex contains small bits of aluminium which react with caustic soda to produce dihydrogen. What volume of dihydrogen at $20^{0}C$and one bar will be released when $0.15$g of aluminium reacts?

• A. 204 mL
• B. 200 mL
• C. 203 mL
• D. 400 mL

Answer 1

Answer: (C)

203 mL

Answer 2

: The reaction between aluminium and caustic soda is

$\underset{2 \times 27 = 54g}{2Al +}2NaOH + 2H_{2}O \rightarrow 2NaAlO_{2}\underset{3 \times 22.4LatSTP}{+ 3H_{2}}$

$\therefore$54g of Al produces $H_{2}atSTP = 3 \times 22.4L.$

$0.15$g of Al will produce $H_{2}atSTP$

$= \frac{3 \times 22.4}{54} \times 0.15 = 0.186L$

At STP Given conditions

$P_{1} = 1atm$ $V_{1} = 0.186L$ $V_{2} = ?$

$T_{1} = 273K$ $T_{2} = 273 + 20 = 293K$

Applying ideal gas equation $\frac{P_{1}V_{1}}{T_{1}} = \frac{P_{2}V_{2}}{T_{2}}$

$\frac{1 \times 0.1867}{273} = \frac{0.987 \times V_{2}}{293}$

$V_{2} = \frac{293}{0.987} \times \frac{1 \times 0.1867}{273} = 0.2030L = 203mL$