Chemical Reactions Between 6M of HCL & a Piece of Calcium

In chemistry lab experiments, you must consider all possible reactions.
••• laboratory image by Oleg Verbitsky from

When a piece of calcium is placed into a solution of hydrochloric acid, it undergoes two vigorous reactions. However, the reactions that occur when HCl is dissolved in water (H2O) form the basis for understanding the reactions that occur when calcium (Ca) is placed into a diluted solution of aqueous hydrochloric acid [i.e., 6M HCl (aq)].

Initial Dissociation or Acid-Base Reaction

It is important to remember that hydrochloric acid is not simply a mixture of HCl and H2O. When HCl is dissolved in water this strong acid completely dissociates. When HCl is added to H2O, the dissociation reaction frees the H+ ion which bonds with H2O to form hydronium ions (H3O+) and leaves free Cl- ions in solution. This reaction eventually reaches an equilibrium, and the increase in H3O+ ions decreases pH, resulting in an acidic solution that can be verified with litmus paper. In diluted solutions such as 6M HCl, water molecules also remain.

Formation of Calcium Hydroxide

When calcium (Ca2+) is added to dilute 6M HCl solution, the Ca2+ reacts with H3O+ ions and water molecules (H2O) vigorously to form calcium hydroxide (CaOH2) and hydrogen gas (H2). This reaction generates heat and results in the release of bubbles of H2 gas. The CaOH2 will appear as a whitish film on the water. The formation of CaOh2 reduces the number of H3O+ ions in the solution and increases the pH of the solution--litmus paper tests verify this change in pH.

Formation of Calcium Chloride

When Ca is added to 6M HCl solution, the Ca also combines with free Cl- in the solution to form calcium chloride (CaCl2). This acid salt will precipitate to the bottom of the test beaker.

Related Articles

How to Do Net Ionic Equations in Chemistry
Sulfuric Acid & Chlorine Bleach Reaction
How to Test for Hydrochloric Acid
How to Dissolve Calcium Oxalate
How to Calculate Solubilities
The Effects of NaOH Concentration with H2O
How to Test the Completeness of Precipitation of an...
How to Find Mass Percentage
How to Test for Calcium Hydroxide
How to Make Sodium Nitrate
Why Does Phenolphthalein Change Color?
How to Dissolve Magnesium Chloride
How to Make an EDTA Solution
How to Calculate the Concentration of Ions in a 0.010...
Facts About Calcium Chloride
How to Mix Calcium Chloride and Water
Strong vs Weak Acids and Bases
How to Find the Number of Moles Needed to React
The Effect of Vinegar on Chicken Bones
Potassium Permanganate Experiments