Magnesium carbonate and Hydrochloric acid | MgCO3 + HCl

When aqueous hydrochloric acid (HCl) is mixed with solid Magnesium carbonate, it will give carbon dioxide, magnesium chloride and water as results. Magnesium carbonate is insoluble in water and exists as a white precipitate. But when reaction proceeds, you can see white precipitate dissolves and gives a colourless aqueous solution.





In this tutorial, we will discuss followings.

Stoichiometric balanced equation of MgCO3 and HCl reaction Physical state,pH and colour changes



Stoichiometric balanced equation of MgCO3 and HCl reaction


MgCO3(aq) + 2HCl(aq) → MgCl2(aq) + CO2(aq) + H2O(l)

To react with one mole of magnesium carbonate, two moles of hydrochloric acid is required. As a result, one mole of carbon dioxide, one mole of magnesium chloride and one mole of water are given.


magnesium carbonate hydrochloric acid MgCO3 + HCl


Physical state and colour changes

Here, we will discuss how following parameters are changed during the reaction.

  • Physical status and colour changes
  • pH


Physical status and colour change

Because MgCO3 is insoluble in water, it exist as a precipitate. HCl acid is colourless solution. During the reaction, you can observe tiny carbon dioxide gas bubbles are formed in the solution. When all MgCO3 reacts with HCl, you will see a colourless aqueous solution.



pH change

The aqueous solution which contains MgCO3 is slightly alkaline due to presence of carbonate ion (CO32-) and may show pH value just higher than 7. Because, HCl is a strong acid, it's pH value is well below than 7.

When all MgCO3 and HCl are consumed, there is MgCl2 and CO2 except H2O. Because Mg2+ ion and Cl- ions are stable in water, they do not participate in any hydrolysis process. Therefore, no any acidic or basic properties caused due to Mg2+ ions and Cl- ions. But, if some CO2 gas is remaining in solution, it can give a slightly acidic solution due to formation of weak acid, carbonic acid.



Can I identify magnesium carbonate from calcium carbonate from this reaction?

No, because both calcium carbonate and magnesium carbonate react with Hydrochloric acid and emit carbon dioxide gas. Also both reactions give colourless aqueous solutions. So, we are unable to identify magnesium carbonate from calcium carbonate.



Safety and health hazards possible due to this reaction



Questions



You are provided 4.2g of solid pure magnesium carbonate and 100 cm3 of aqueous 0.1 mol dm-3 HCl solution. When aqueous HCl solution and solid MgCO3 are mixed with each other, how much amount (mol) of carbon dioxide gas is evolved?

Here, we will solve this problem in several steps.


Step 1: Calculate amount of reactants.


  • Amount of MgCO3 = 4.2 g/ 84 g mol-1
  • Amount of MgCO3 = 0.05 mol

  • Amount of HCl = 0.1 mol dm-3 * 100 * 10-3 dm3
  • Amount of HCl = 0.01 mol

Deciding limiting reagent

According to the balanced equation, 2 moles of HCl are required to react with 1 mol of MgCO3. Therefore, 0.1 mol of HCl is required to react with 0.05 mol of MgCO3. But, there is only 0.1 mol of HCl available to react with 0.05 mol of MgCO3. So, all HCl is consumed and HCl is the limiting reagnt in this reaction.


Generated CO2 amount

0.005 mol of CO2 gas is generated.







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