This document describes a laboratory experiment to measure the amount of antacid needed to neutralize hydrochloric acid. Students will add increasing amounts of antacid powder to 50mL of dilute hydrochloric acid while monitoring the color change of an indicator from red to orange, which indicates neutralization. They will record the mass of antacid used and compare results with other groups. Questions address calculating the amount of antacid needed for larger volumes of acid. The aim is to observe the neutralization reaction between an acid and base.

1. NEUTRALISATION
Y E A R 1 0 – A C I D S A N D I N D I C AT O R S
G.Ajetrao

2. AIM
Aim: To measure how
much antacid is needed to
neutralise some
hydrochloric acid.

3. BACKGROUND INFORMATION
• Neutralisation is a reaction
in which an acid and a base cancel
each other out to form a salt and water.
To neutralise an acid you add a base, and to neutralise a base
you add an acid.
• acid + base → salt + water
• There are many applications of neutralisation in everyday life.
For example, the odour of fish and other seafood is due to
bases called amines. Adding lemon juice or vinegar, which is
acidic, neutralises the amines, giving a more pleasant smell.

4. EQUIPMENT
1. Dil Hydrochloric acid
(0.1M)
2. Small conical flask
(250mL)
3. Measuring cylinder
(50mL)
4. Methyl orange indicator
5. Spatula
6. Antacid powder/ crushed
tablet.
7. Plastic petridish/paper
8. Electronic balance
9. White paper

5. RISK ASSESSMENT
Risk
Acids are corrosive
Injury
Burns and irritation if in
contact with skin .
Prevention
Measure dil HCl carefully.
Wear safety goggles

6. METHOD
1. Clean the petridish.
2. Measure the mass of 1spatula full (level) of powdered
antacid using an electronic balance. ( weigh a piece of small
paper or a plastic petridish / or use tare button to make the
paper weight zero, then add powdered antacid)
3. Record the weight of antacid in a result table.
4. Use a measuring cylinder to measure out 50 mL of dilute
hydrochloric acid.
5. Pour the acid into the flask.
6. Add 3 – 4 drops of methyl orange indicator to the acid.

7. METHOD
7. Place a sheet of white paper under the flask.
8. Use the spatula to add antacid bit by bit to the acid.
9. Swirl the flask gently to stir the mixture.
10. Stop adding antacid when the colour changes from red to
orange.
11. Measure the mass of the unused antacid using electronic
balance.
12. Find the mass of antacid used to neutralise 50 mL of dil HCl
by subtracting the mass of unused antacid from the original mass
of the antacid .
13. Record the data in result table.

8. RESULTS
• Take a picture of the before and after result of neutralisation
reaction and upload the picture to your experimental report.
• Mass of petridish + powdered antacid = _________ (m1)
• Mass of petridish + unused antacid = ___________ (m2)
• Mass of antacid used to neutralise dil HCl = m1 – m2
•
=

9. DISCUSSION
• Write an appropriate discussion.

10. CONCLUSION
• Write an appropriate conclusion

11. QUESTIONS
1. How much antacid was needed to neutralise 50 mL of dilute
HCl?
2. Compare your results with other groups. How accurate do you
think your measurement was? Explain your answer.
3. If your stomach contained 1 L of dilute HCl, how much
antacid powder would you need to neutralise it?