A 0.563 g sample of a solid carbonate MCO is heated strongly in an open crucible
CHEMISTRY · Multi-part · A Level · Chemistry · Amount of substance · Amount of substance
Problem
A 0.563 g sample of a solid carbonate MCO3 is heated strongly in an open crucible. The decomposition reaction
MCO3(s) ⟶ MO(s) + CO2(g)
proceeds to completion. After cooling, the mass of solid residue is 0.269 g.
Assume no other reactions occur and that no mass is lost from the crucible except CO2.
(a) Determine the number of moles of CO2 that escaped during the decomposition.
(b) Calculate the atomic mass of the metal M.
(c) Identify the element M, and write the complete electron configuration for its gaseous atom in the ground state.
(d) Justify why the carbonate of this element adopts a 1:1 stoichiometry (MCO3) rather than another possible ratio, linking your reasoning to charge balance and valence-electron considerations.