Question

4.9 g of potassium chlorate when heated produced1.92 g of oxygen and the residue left behind weighed 2.96 g.Show that these results illustrates the law of conservation of mass.

Please explain nicely.​

Answer 1

According to the equation

2KClO3->2KCl + 3O2,

245g of Potassium chlorate gives 149g of Potassium chloride and 96g of Oxygen gas

but by using only 4.9g of Potassium chlorate we get

KCl= (4.9×149)/245 = 2.98g of KCl.

Also for calculating amount of Oxygen,

O2= (4.9×96)/245= 1.92g of O2 gas

hence no Oxygen was lost

so, 4.9-(2.96+1.92)= 0.2g

By calculation, we know that 0.2g of KCl was lost and not Oxygen gas

this 0.2g of KCl is supposed to have sublimed during the reaction.

Hence mass is conserved.