Question

If atomic mass of mg is 24g .find out the volume of H2 collected at STP when 12g of mg react with acid to form MgSO4.

Answer 1

Given:

The Atomic mass of Mg is 24g , only 12g is used for the reaction.

Magnesium is reacting with acid to form MgSO4 (Magnesium Sulphate)

To Find:

Volume of H2 collected at STP.

Solution:

Chemical Reaction:

Mg + H2SO4 -----> MgSO4 + H2(gas)

1) one mole of magnesium = 24 g , since only 12g is used in the reaction that  implies only half a mole i.e (0.5 mole) of magnesium is used .

2)STP Implies Standard Temperature and Pressure therefore pressure = 1 bar and temperature = 373K and volume = 22.4L (STP conditions)

3)At STP conditions 1 mole of any compound / gas gives 22.4L in STP conditions .

4) Since one mole implies 22.4L of the volume collected , Therefore half a mole i.e (0.5m mole) implies $\frac{22.4}{2}$L at STP.

5) On solving we get the answer as 11.2 L.

Therefore when 12g of Magnesium reacts with acid 11.2L of H2 is collected when STP conditions are applied .