Question

In a reacting flask, 500 cm3 hydrogen is mixed with 500 cm3 oxygen and is ignited. (a) Which reactant is the limiting reagent? (b) Calculate the mass of water formed.

Answer 1

Answer:

See Explanation

Explanation:

From Gay-Lussac's law of combining volumes;

Equation of the reaction; 2H2(g)  + O2(g) -------> 2H2O(g)

Ratio of volumes;              2           :    1                :    2

Initial volumes;                  500cm^3   500cm^3       0 cm^3

Reacting volumes;          500cm^3    250cm^3      500cm^3

Final Volumes;                0 cm^3        250 cm^3     500 cm^3

We can easily see from the table that the limiting reactant is oxygen.

Hence, the mass of water formed is obtained from;

1 mole of gaseous water occupies 22400 cm^3

x moles of water occupies 500cm^3

x = 500cm^3 * 1 mole/22400 cm^3

x = 0.022 moles of water

Mass of water = 0.022 moles of water * 18 g/mol

Mass of water = 0.396 g