Which products would result from the double replacement reaction between mgcl2 (aq) and na2co3 (aq) ?

Double displacement reactions are when the cations and anions of 2 compounds are exchanged. Cation of one reactant will form a new product with the anion of the other reactant and vice versa.

MgCl₂ - - > Mg²⁺ + 2Cl⁻

Na₂CO₃ - - > 2Na⁺ + CO₃²⁻

the cations and anions are exchanged therefore double displacement reaction is as follows;

MgCl₂ (aq) + Na₂CO₃ (aq) - - > MgCO₃ (s) + 2NaCl (aq)