Question

Calculate the mass of O2 produced if 10.00g sodium chlorate is completely decomposed by heating.

Answer 1

2 KClO3 -------> 2KCl + 3 O2

1) M(KClO3) = 39.1 +35.5+3*16.0 = 122.6 g/mol

2) Number of moles of KClO3:

10.00g *1mol/122.6 g= 10.00/122.6 mol KClO3

3) 2 KClO3 -------> 2KCl + 3 O2

from equation 2 mol 3 mol

given 10.00/122.6 mol x mol

x = (10.00*3)/(2*122.6) mol O2

4) Molar mass O2

M(O2) = 16.0*2= 32 g/mol

5) Mass of O2:

(10.00*3)/(2*122.6) mol O2 *32 g/1 mol = (10.00*3*32)/(2*122.6) = 3.915 g O2