Question

A mass of 3.462 g of a metal carbonate, MCO3, is heated to drive off carbon dioxide. The remaining metal oxide has a mass of 2.229 g.
MCO3(s) → MO(s) + CO2(g)
What is the identity of the metal?

Answer 1

Ans :

Mass of CO2 = mass of MCO3 - mass of MO

= 3.462 g - 2.229 g

= 1.233 g

Number of mol of CO2 = 1.233 / molar mass

= 1.233 / 44.01 = 0.028 mol

So the number of mol of MCO3 and MO will also be 0.028 mol

Now 0.028 mol MO will have 0.028 mol M and 0.028 mol O

Mass of O in MO = mol x molar mass

= 0.028 x 15.999 = 0.448 grams

Mass of M in MO = mass of MO - mass of O

= 2.229 - 0.448

= 1.78 g

Molar mass of M = mass / number of mol

= 1.78 / 0.028

= 63.6 g/mol

This corresponds to the molar mass of metal copper.

So the identity of metal is Copper (Cu).