Reactions involved:
Mg(OH)2(s) + 2HCl(aq) MgCl2(aq) +2H2O(l)
Al(OH)3(s) +3HCl(aq) AlCl3(aq) +3H2O(l)
NaOH(aq) +HCl(aq) NaCl(aq) + H2O(l)
Brands we have chosen:
- ACTAL plus anti-acid tablet
Contents: Aluminium Hydroxide 200mg
Magnesium Hydroxide 150mg
Simethicone* 25mg
- Hydrosil Tab
Contents: Aluminium Hydroxide 200mg
Magnesium Hydroxide 200mg
Simethicone 20mg
- Maalox Plus Tab
Contents: Aluminium Hydroxide 200mg
Magnesium Hydroxide 200mg
Simethicone 25mg
- Magsil
Contents: Aluminium Hydroxide Dried Gel 200mg
Magnesium Hydroxide 200mg
- Fedra-Gel-S
Contents: Aluminium Hydroxide Dried Gel 200mg
Magnesium Hydroxide 200mg
Simethicone 30mg
* Simethicone is an anti-foaming agent that decreases the surface tension of gas bubbles, causing them to form larger bubbles in the stomach that can pass through the oesophagus easily by burping.
Some calculations involved before designing the experiment:
No of mol of OH- in one tablet: 0.2x3 + 0.2x2
26.98+(16.0+1.0)x3 24.3+(16.0+1.0)x2
= 0.014555
No of mol of H+ required: 0.014555
No of mol of HCl required: 0.014555
Since No of mol= Molarity x Volume,
Volume of HCl: No of mol
Molarity
= 0.014555
1
= 0.014555 dm3 = 14.6 cm3
∴ The minimum amount of 1M HCl required to dissolve all the OH- inside one anti-acid tablet is 14.6 cm3.
∵ The 0.1 M NaOH used should be in the range of 15 – 40 cm3.
Let x be the added amount of 1M HCl.
(x-0.0146) × 1 × 10 ÷ 250 = 0.040 × 0.1
x = 0.1146
∴ The amount of 1M HCl added should be around 100cm3.
Chemicals and Apparatus required:
Chemicals required:
- 1M HCl (aq)
- 0.1M NaOH (aq)
- Different brands of anti-acid tablets
- Phenolphthalein
Apparatus required:
- Wash bottle
-
10 cm3 and 25cm3 Pipette
- Pipette filler
- Burette
-
250cm3 Volumetric flask
- Conical flask
- Filter funnel
- 250ml Beaker
- Glass rod
- Clamp and stand
- White tile
- Mortar and Pestle
Procedures:
- Crush one tablet into powder form with pestle and mortar.
-
Transfer the crushed sample to a 250cm3 beaker.
-
Wash a 25cm3 pipette with distilled water then the 1M HCl.
-
Pour in 100cm3 of 1M HCl by the washed pipette to dissolve all crushed sample.
-
Pour the mixture into a 250cm3 volumetric flask washed with distilled water. Add distilled water into the flask until it reaches the graduation mark. Invert the flask for several times.
-
Wash a 10cm3 pipette with distilled water then diluted solution. Transfer 10cm3 of the solution into a conical flask.
- With the use of the filter funnel, rinse the burette with distilled water and then with 0.1M NaOH.
- Fill the burette with 0.1M NaOH. Record the initial reading of the burette.
- Add a few drops of phenolphthalein into the conical flask.
- Run the 0.1M NaOH into the conical flask until the solution turns from colourless to permanent pink.
- Record the final reading of the burette.
- Repeat the above steps several times to obtain a mean titre.
- Repeat the whole process by using different brands of anti-acid tablets.
Calculations:
Mean titre of NaOH used: V1
No of mol of OH- used: V1 × Molarity (0.1M)
= 0.1V1
No of mol of H+ used to react with OH-: 0.1V1
No of mol of H+ left after the neutralization with the anti-acid tablet:
0.1V1 × 250 ÷ 10 = 2.5 V1
No of mol of H+ used by the anti-acid tablet: Total no of mol of HCl used –2.5 V1
= 100 –2.5 V1
No of mol of OH- in each anti-acid = No of mol of H+ used = 100 –2.5 V1