0.048 g of magnesium was reacted with excess dilute Hydrochloric acid at room temperature & pressure. The hydrogen gas given off was collected.
Which apparatus could be used to carry out this experiment and collect the hydrogen gas?
The experiment could be done in a Wolff's bottle fitted with an exit tube and a long neck funnel. The other end of the exit tube should be bent and trapped under water. A gas jar of 0.05 Lit. capacity, filled with water has to be inverted over that end. The hydrogen gas will be collected at the gas jar through downward displacement of water. The volume of gas ollected can be calculated by considering the stoichiometries
Mg + 2HCl react to produce MgCl2 + H2 (g)
24 g or one gm-atom Mg produces 22.4 lit H2 (g) at NTP
0.048 g Mg produces 22.4*0.048/24 = 0.0448 lit H2 (g) at NTP
Now at Room temp (higher than NTP), this gas will expand and the final volume can be obtained from gas law eqn. V/T = constant
so V1/T1 = V2/T2
or 0.0448/273 = v/298
or v= 0.0448*298/273 = 0.0489 Lit. = 0.05 lit. (approx.)