Question

magnesium and oxygen combine in the ratio of 3:2 by mass to form magnesium oxide . how much oxygen is required to react completely with 12g of magnesium?

Answer 1

8 gram of oxygen is required

Given,

ratio = 3:2

oxygen is required to react completely with 12g of magnesium =?

Using law of constant proportion and given ratio it is clear that

3g of Magnesium reacts with 2g of Oxygen.

⇒ 1g of Magnesium reacts with $\bold{\mathff{\dfrac{2}{3}}}$ g of Oxygen.

∴ 12g of Magnesium reacts with $\bold{\mathff{\dfrac{2}{3}\times 12g}}$of Oxygen.

⇒ Amount of oxygen needed = $\bold{\mathff{\dfrac{2}{3}\times 12g}}$

or , 8g

∴ 8 gram of oxygen is required