When sodium hydroxide (NaOH) and hydrochloric acid (HCl) are mixed, they undergo a neutralization reaction that produces water and a soluble salt. The reaction occurs because the sodium hydroxide, a strong base, and hydrochloric acid, a strong acid, neutralize each other’s properties, resulting in a solution that is neither acidic nor basic. To separate the soluble salt from the solution, the mixture is filtered to remove any impurities or precipitates, and then the filtrate is evaporated to dryness in an evaporating dish. The resulting dry white powder is the soluble salt, which can be weighed and compared to the theoretical yield calculated using stoichiometry. By understanding the process of neutralization and separation of soluble salts, scientists can investigate the stoichiometry of acid-base reactions and determine the yield of a reaction.
Aim: To investigate the neutralization of hydrochloric acid with sodium hydroxide and to separate a soluble salt.
Materials:
- Hydrochloric acid (HCl) 1mol dm-3
- Sodium hydroxide (NaOH) 1mol dm-3
- Distilled water
- Phenolphthalein indicator
- Beaker
- Burette
- Pipette
- Filter paper
- Funnel
- Bunsen burner
- Tripod stand
- Wire gauze
- Evaporating dish
- Activated Charcoal
Procedure:
- Rinse a burette with distilled water and then with hydrochloric acid to remove any impurities. Fill the burette with hydrochloric acid up to the 0.00 mL mark.
- Use a pipette to measure 25 mL of sodium hydroxide solution and pour it into a beaker.
- Add 2-3 drops of phenolphthalein indicator to the sodium hydroxide solution.
- Place the beaker on a tripod stand and heat it using a Bunsen burner.
- While stirring the solution, add hydrochloric acid drop by drop from the burette until the phenolphthalein indicator changes from pink to colorless. This indicates that the acid has been neutralized.
- Once the solution has been neutralized, add a small amount of activated charcoal to the beaker while stirring continuously.
- Filter the solution through a funnel and filter paper to remove the activated charcoal and any remaining impurities.
- Pour the filtrate into an evaporating dish and heat it over a Bunsen burner until all the water evaporates, leaving behind a dry white powder.
- Weigh the evaporating dish with the dry powder and record the mass.
- Calculate the mass of the soluble salt by subtracting the mass of the evaporating dish from the total mass.
- Record the mass of the soluble salt and compare it with the theoretical yield calculated using stoichiometry.
Results:
- Volume of hydrochloric acid used to neutralize sodium hydroxide solution: __ mL
- Mass of evaporating dish: __ g
- Mass of evaporating dish with dry powder: __ g
- Mass of soluble salt: __ g
Discussion: The addition of activated charcoal to the solution helps to remove the phenolphthalein indicator, which could interfere with the measurement of the mass of the soluble salt. The charcoal absorbs the indicator and other impurities, allowing for a clearer solution to be filtered and evaporated.
The rest of the procedure remains the same, with the soluble salt being separated from the solution using filtration and then dried in an evaporating dish. The mass of the soluble salt can be compared with the theoretical yield calculated using stoichiometry to determine the efficiency of the reaction.
Practical Science 