Question

The drain cleaner, drainex contains small bit of aluminium which react with caustic soda to produce dihydrogen. What volume of dihydrogen at 20°C and are bar will be released when 0.15 g of aluminium reacts.

Answer 1

Aluminium reacts with caustic soda (NaOH) in accordance with the reaction.

2Al (s) + H₂O + 2NaOH → 2NaAlO₂ + 2H₂ (g)

2 x 27 g                                                3 mol

= 54 g                                              3 x 22.4 L

Volume of hydrogen (at STP) released when 0.15 g of Al reacts

= {0.15 g}/{54 g} x 3 x 22.4 L

= 0.187 L = 187 ml

p₁ = 1 bar p₂ = 1 bar

T₁ = 273 K T₂ = 20°C = (20 + 273)K

= 293 K

V₁ = 187 mL V₂ = ?

Pressure is held constant, therefore, using the relationship