Titration of Hydrochloric Acid against Standard Sodium Carbonate

Methods of acid-base titration based on a sample dissolution exceeding normal acid, followed by back titration with a standard base is characterised in this experiment. Using bromophenol blue as an indicator, hydrochloric acid solutions were standardised against pure sodium carbonate. Here, we will study the titration of HCl and sodium carbonate in detail.

Aim

Determination of the strength of the diluted hydrochloric acid solution by titrating it against the normal sodium carbonate solution (M/10).

Theory

The hydrochloric acid solution can be titrated using a methyl orange indicator against the sodium carbonate solution. If a slightly acidic solution is titrated with a weak base, the endpoint is slightly acidic. The solution is slightly basic if a weak acid is titrated with a strong base since the salt produced is to a certain degree hydrolyzed. The reaction of sodium carbonate with HCl is given below.

Na₂CO₃(aq) + 2HCl(aq) → 2NaCl(aq) + CO₂(g) + H₂O(l)

CO₃2-(aq) + 2H+(aq) → CO₂(g) + H₂O(l)

These are the hydrochloric acid and sodium carbonate equations.

In acid-base titrations, the amount of the acid becomes chemically equivalent to the amount of base present. The solution becomes neutral in the event of a strong acid and a strong base titration of the solution.

Materials Required

1. Burette

2. Pipette

3. Conical flask

4. Burette stand

5. Funnel

6. Stirrer

7. White glazed tile

8. Measuring flask

9. Hydrochloric acid

10. Sodium carbonate

11. Methyl orange

12. Watch glass

Procedure for Titration of HCl and Sodium Carbonate

A. Preparation of a Sodium Carbonate Standard Solution

1. Sodium carbonate has a molecular weight of 106.

2. The amount of sodium carbonate needed to make a 250mL solution is 1.325g.

3. Prepare the standard solution by dissolving 1.325g of sodium carbonate in distilled water and adding the required amount of water to a 250ml measuring flask.

B. Titration of Hydrochloric Acid and Sodium Carbonate Solution

1. Wash, rinse, and fill the burette with M/10 Na₂CO₃ solution. Note the initial reading.

2. Take 10cm³ of HCl solution with the help of a pipette and transfer it into a clean washed titration flask.

3. Add 2 drops of methyl orange into the titration flask.

4. Add M/10 sodium carbonate solution to the titration flask till the colour changes to light pink.

5. Note the final reading and find out the volume of sodium carbonate solution used to neutralise the HCl solution.

6. Repeat the experiment till you get concordant readings.

Observation

Volume of HCl solution = 10cm³.

The volume of sodium carbonate solution used = V cm³.

Calculation

(Sodium carbonate) a₁M₁V₁ = (HCl) a₂M₂V₂.

2 × 1/10 × V = 1 × x × 10 x = V/5 Strength in g/L = molarity × molar mass = V5 × 36.5.

Result

The strength of the hydrochloric acid solution is ________ g/L.

Precautions

1. Do not spill the material on the balance pan while measuring.

2. Gently turn the balance knob.

3. After weighing, put the weights in the weights box in the correct positions.

4. Wash the watch glass thoroughly to ensure that not a single crystal remains on it.

5. When moving the weighted substance, bring the watch glass close to the funnel and gently move it. It should be washed multiple times with distilled water.

6. After the titration, wash the burette with water.

7. To prevent applying distilled water above the mark on the neck of the measuring cylinder, the last few drops should be applied with a pipette.

Did You Know?

• Hydrochloric acid, also known as muriatic acid, is a hydrogen chloride aqueous solution. It's a colourless liquid with a strong, pungent odour. It's considered a strong acid. In the digestive systems of most animal species, including humans, it is a component of gastric acid. Hydrochloric acid is a common laboratory reagent as well as a common industrial chemical.

• The boiling and melting points, density, and pH of hydrochloric acid are all influenced by the concentration or molarity of HCl in the aqueous solution. They range from values for water at very low concentrations near 0 percent HCl to over 40 per cent HCl for fuming hydrochloric acid.

• Hydrochloric acid is produced by dissolving hydrogen chloride in water in an industrial environment. Hydrogen chloride can be produced in a number of ways, but there are some precursors to hydrochloric acid. In the chlor alkali process, which produces hydroxide, hydrogen, and chlorine, the latter of which can be combined to produce HCl, large-scale production of hydrochloric acid is almost always incorporated with industrial-scale production of other chemicals.

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