Question

Calculate the volume of oxygen at 15°c and 745mmhg which could be obtained by heating 10g of potassium trioxochlorate. ( K =39, Cl=35.5, O=16. Molar mass of gas at STP=22.4dm3

Answer 1

$$2KClO_3 = 2KCl + 3O_2$$

$$n (KClO_3) = m/M = 10/122.5 = 0.082mol$$

$$n(O_2) = 3/2 * 0.082 = 0.123mol$$

$$V(O_2) = n*V_m = 0.123*22.4 = 2.755dm^3$$

From the combinated gaseous law:

$$V^`(O_2) = {T_2p_1V(O_2) \over T_1p_2}$$

$$V^`(O_2) = {288.15*760*2.755 \over 273.15*745} = 34.982dm^3 \approx 35dm^3$$

Answer: 35dm³