Question

Q.) 12 g of magnesium powder was ignited in a container having 20 g of pure oxygen. After the reaction was over, it was found that 12 g of oxygen was left unreacted. Show that it is according to law of constant proportions.

2Mg + O2 → 2MgO.

Answer 1

12gm of mg powder does not react with o2 because it will already have an oxygen coating over it. the mass of the reactant (that is 12gm) = to the mass of the product(12gms) therefore it is in constant proportion

Answer 2

Answer:

amu of oxygen is 16u

amu of mg is 24

so ,

2 x 24u + 2 x 16u  

= 48u + 32u

so according to the q uestion,

12 g of Mg and 8g of O

so if we compare the ratios,

48:32, 12:8

both of their simplified ratios come to 4:3

There! You have it! :)))