MgCO3 + 2 HCl --> MgCl2 + CO2 + H2O. KMnO 4 + HCl = KCl + MnCl 2 + H 2 O + Cl 2; K 4 Fe(CN) 6 + H 2 SO 4 + H 2 O = K 2 SO 4 + FeSO 4 + (NH 4) 2 SO 4 + CO; ... Give us feedback about your experience with chemical equation balancer. MgCO3 + 2HCl --> H2CO3 + MgCl2. Because of its low solubility in water and hygroscopic properties, MgCO 3 was first added to salt in 1911 to make it flow more freely. 100.0 mL of 2.45 M MgCO3 is 0.245 mole of MgCO3. The decomposition looks like this. MgCO3(s) + 2HNO3(aq) → Mg(NO3)2(aq) + CO2(g) + H2O(l) It's Mg(NO3)2 (and not MgNO3) because the magnesium ion has a charge of +2, and so you need two nitrate ions to equalize the charge (because NO3 ions only have a charge of -1). Since two mole of HCl may completely react with one mole of MgCO3, 0.245 mole of MgCO3 is the limiting reactant. Put them both together and we have your reaction. The catch is that H2CO3 (carbonic acid) molecules don't exist in aqueous solution, so it is questionable whether they actually every form in the first place. The Morton Salt company adopted the slogan "When it rains it pours" with reference to the fact that its MgCO 3-containing salt would not stick together in humid weather. I know this confuses some people. H2CO3 --> CO2 + H2O. 2HCl + MgCO3 --> MgCl2 + CO2 + H2O. 225.0 mL of 2.30 M HCl is 0.518 mole of HCl.