In an experiment 1.015 g of a metal carbonate, containing an unknown metal M, is heated to give the metal oxide and 0.361 g CO2.

Question

MCO3(s) + heat MO(s) + CO2(g)
What is the identity of the metal M?

Answer 1

mass MO = 1.015 - 0.361 = 0.654 g
moles CO2 = 0.361/44 = ??
moles MO = same as mols CO2.]
moles = grams/molar mass.
You have moles and grams, solve for molar mass of MO, then subtract 16 from that to arrive at the atomic mass M.