Which compounds are electrolytes

Can anyone (a-level) a student was analysing a carbonate compound, mco3, containing an unknown group 2 metal, m. the student carried out thermal decomposition on 0.730g of the carbonate and measured the volume of gas produced. mco3 (s) mo (s) + co2 (g) the student collected and measured 120cm3 of carbon dioxide. 1 mol of carbon dioxide occupies 24 000 cm3 under these conditions. calculate the molar mass of the group 2 carbonate and hence deduce the identity of the group 2 metal, m.

Write the complete balanced equation for the reaction between lead (iv) oxide (pbo2) and water (h2o).

What are the similarities of physical and chemical change ?