Question

A metal, M, forms a nitride compound with the formula M3N2. This compound is 84.78 % M by mass and 15.22 % N by mass. Calculate the molar mass of the metal, M.

Answer 1

Answer – We are given, compound formula = M₃N₂

Mass percent of M = 84.78 %, for N = 15.22 %

Assume 100 g of sample, so mass of metal, M = 84.78 g

And mass of N = 15.22 g

We know mole ratio of M to N in the formula is 3:2

First we need to calculate the moles of N

Moles of N = mass of N / molar mass of N

                = 15.22 g / 14.007 g.mol^-1

                = 1.0866 moles

Now from the mole ratio in the compound formula

2 moles of N = 3 moles of M

So, 1.0866 moles of N = ?

= 1.0866 moles of N * 3 moles of M / 2 moles of N

= 1.6298 moles of M

Molar mass of M = mass of M / moles of M

                         = 84.78 g / 1.6298 moles of M

                         = 52.015 g/mol

So molar mass of metal, M is 52.015 g/mol