The mass of potassium chloride is 3.8 g . Look at the mole ratio you have between potassium chlorate and potassium chloride; what you will see is that every 2 moles of potassium chlorate will produce 2 moles of potassium chloride, i.e. you have a 1:1 mole ratio between the two compounds
The particle theory is used to explain the properties of solids, liquids and gases. The strength of bonds (attractive forces) between particles is different in all three states.