2. The HCl (aq) solution has a lower concentration than what is indicated on the

Question

2. The HCl (aq) solution has a lower concentration than what is indicated on the reagent bottle. Will this result indicate the presence of more or fewer moles of base in the antacid? Explain.

3. All of the CO2 is not removed by gently boiling after the addition of HCl. Will the reported amount of antacid in the sample be too high, too low, or unaffected? Explain. (Hint: Remember that CO2 (g) is an acidic anhydride.)

6. The Bromophenol Blue endpoint is surpassed in the back titration of the excess HCl with the sodium hydroxide titrant. As a result of this technique error, will the reported amount of antacid in the samole be too high, too low, or unaffected? Explain.

Explanation / Answer

3. if you do not expell the CO2, it will be in the form of H2CO3 in this excess HCl solution.

they will both react with the NaOH

the hope was that the acid H2CO3 would not be a factor, that heating would convert it into CO2 & H2O, that the CO2 would be expelled, and that the NaOH would only react with the excess HCl

but you will be using some NaOH to destroy the H2CO3 as well. this takes additional NaOH

it implies incorrectly that there was a large excess of HCl

it implies incorrectly that there was so much excess HCl because the antacid tablet was too weak

I believe your answer is: the reported amount of antacid in the sample is too low

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