Reagent Concentration, moles per litre (M)
Sodium hydroxide – NaOH (aq) 0.500
Hydrochloric acid – HCl (aq) 0.500
Methyl orange – C14H14N3NaO3S (l)Experiment 1 Experiment 2
Mass used of tablet 1.246 g 1.201 g
Concentration of hydrochloric acid (HCl) 0.50 mol dm-3
0.50 mol dm-3Volume of HCl added to the flask 0.0400 dm3
0.0400 dm3 Number of moles of HCl added 0.2 moles 0.2 moles
Concentration of NaOH (sodium hydroxide) 0.50 mol dm-3
0.50 mol dm-3 Volume of NaOH added to the flask 0.0100 dm3
0.0100 dm3 Number of moles of HCl reacted with NaOH 0.005 moles 0.005 moles
Moles of HCl neutralised by antacid 0.0395 moles 0.0395 molesTitration of sodium hydroxide (NaOH)Experiment 1 Experiment 2
Final volume (ml) 40.00 40.00
Initial volume (ml) 0.80 30.5
Volume used (ml) 39.2 9.5Calculations
You should include all calculations.
Make sure all steps are shown in your sample calculation.
Any formulas used should be shown and explained.
+ balanced equationAnalysis In your discussion, you should address the following points:Explain the chemistry behind the two reactions that have occurred giving any relevant equations.What do your results mean in terms of the ‘real neutralising power’ of your antacid? You should refer to your own results.Critique of the experimental design including sources of uncertainty. What are the sources of uncertainty present in the experiment and how can these be minimised in future experiments?Title:
Chemical analysis by Acid-base titration
Antacid tablet:
A consumer has made a complaint to you that a medicine they have been taking
for digestion problems is not effective at reducing the symptoms of acid reflux
despite the promises made on the packing by the manufacturer that the product
is capable of neutralizing twenty times its weight of stomach acid. You are to
investigate the complaint by finding out the real neutralizing power of the
antacid in question.
The acid neutralizing capacity of a tablet is the amount of hydrochloric acid that
it can neutralize. The capacity can be determined by a technique called back
titration. A known amount of antacid is dissolved in an excess of HCI, and then
the excess acid is back titrated with standardized NaOH solution. When the
endpoint is reached, the number of moles of acid that was added to the antacid
sample is equal to the number of moles of base present, NaOH plus the antacid.
Therefore, the number of moles of HCl that was neutralized by the antacid is
equal to the total number of moles that were neutralized by the NaOH.
Aim:
The objective of this experiment is to figure out the neutralizing power of the
antacid.