4. Analysis of antacid tablets

Question

Tablet mass / g	Start Volume/mL	Finish Volume/mL	Titre/mL
1.30	4.90	21.25	16.35
1.27	21.25	38.60	17.35

From the titration of the antacid tablets, determine the number of moles HCl which have reacted with the tablet, and hence the mass of carbonate in the tablet. Compare this with the manufacturer’s specification (this was 500 mg of calcium carbonate in each tablet).

anybody know how to do this? PLEASE HELP

Answer 1

To answer this completely, one needs to know the concentration of the HCl used, and the weight of each intact tablet before sampling. Then, looking at the balanced equation for this titration, you have....

CaCO3 + 2HCl ==> CaCl2 + CO2 + H2O (NOTE: 2 moles HCl per 1 mole CaCO3)

For titration #1:

moles/L HCl x 0.01635 L x 1 mole CaCO3/2 moles HCl = moles CaCO3 present in 1.30 g of tablet.

Convert this value to grams or mg of CaCO3 using molar mass of CaCO3, and then convert to mg per tablet using the mass of each tablet (data not given). Compare this value to 500 mg/tablet.

Repeat for second titration using 0.01735 L as the volume of HCl.