[yoink]

I got this question on my general chem class.  It is bonus, but I do not know what to do next.  Here is the question.

The active ingredients in an antacid tablet contained only calcium carbonate and magnesium carbonate.  Complete reaction of a sample of the active ingredients required 41.33 ml of 0.08750 M of hydrochloric acid.  The Chloride salts from the reaction were obtained by evaporation from the filtrate from this titration, they weighed 0.1900g what was the percentage by mass of the calcium carbonate in the active ingredients of the antacid tablets?

I know I needed to find the moles of HCl.  Which I got 3.616375 * 10^-4.

This is where I do not know what to do next.

[Borek]

Write reaction equations.

Assume one tablet contains n_Ca moles of calcium carbonate and n_Mg moles of magnesium carbonate. Can you use these unknowns to express number of moles of HCl needed to react with both substances? Can you use them to express mass of chlorides? Goal is to get two equations in two unknowns.

[yoink]

I am still confused.  I need two equations, but which two equations do I need.

[sjb]

How does calcium carbonate react with hydrochloric acid? What about magnesium carbonate?

[yoink]

65.3% that is the answer

[yoink]

or is it 54%?  That is what some of my peers told me they got for the answer.

[Borek]

Something around 65 seems to be correct - I got 66.5%, but I was using very precise molar masses.