Question

0.05g of magnesium when treated with dilute HCl gave 51ml of hydrogen at 27°C and 780 mm pressure .calculate the equivalent mass of magnesium.

please solve it......​

Answer 1

Given:

0.05g of magnesium when treated with dilute HCl gave 51ml of hydrogen at 27°C and 780 mm pressure .

To find:

Calculate the equivalent mass of magnesium.

Solution:

From given, we have,

As 0.05g of Magnesium (Mg) is giving 51mL of Hydrogen gas on reaction with dil. HCl  

So, the number of moles of hydrogen produced is determined by,  

PV = nRT

where, Pressure P = 780 mmHg

Volume V = 51mL = 0.051L

Temperature T = 270C = 300 K

Gas constant R = 62.363 mmHg L mol −1K−1

Therefore, n = PV/RT

= 780×0.051 / 62.363×300

n = 2.126×10−3moles

The mass of Mg reacted to produce 2.126×10−3 moles of Hydrogen = 0.05g  

So, the mass of Mg will react to produce 1 mole of Hydrogen = 0.05/(2.126×10−3) = 23.518g  

Mg displaces two moles of Hydrogen ions so,  

Equivalent mass = Atomic mass/2 = 23.518/2 = 11.759g

Therefore, the equivalent mass of magnesium is 11.759g