CaCO3 + 2HCl ==> CaCl2 + H2O + CO2
mols HCl added initially = M x L = approx 0.0025 but you need a more accurate answer than that estimate. That HCl is more than enough to dissolve all of the tablet and have some HCl left over.
mols NaOH needed to neutralize the excess HCl = M x L = approx 0.0015.
mols HCl used for the tablet is
0.0025-0.0015 = approx 0.0010
Convert mols HCl used in the neutralization of the tablet to mols CaCO3 using the coefficients in the balanaced equation. That will be mols CaCO3 = 1/2 x mols HCl.
Convert to grams in the 0.2455 and then to mg. Then convert to mg in the entire sample.
Post your work if you get stuck.
You weigh out an antacid tablet and determine the mass to be 1.1990 g. After taking a
0.2455 g sample of the antacid tablet, you dissolve it in 25.00 mL of a 0.1006 M solution of hydrochloric
acid in a 250.0 mL Erlenmeyer flask. After heating the solution to get rid of carbon dioxide, you titrate the
leftover hydrochloric acid in the solution in the Erlenmeyer flask with a 0.09913 M solution of sodium
hydroxide and determine that it takes 14.71 mL of the sodium hydroxide solution to react with the leftover
hydrochloric acid in solution. Determine the milligrams of calcium carbonate in the sample of antacid tablet
and then determine the milligrams of calcium carbonate in the entire antacid tablet.
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