one brand of extra-strength antacid tablets contains 750 mg of calcium carbonate

Question

one brand of extra-strength antacid tablets contains 750 mg of calcium carbonate (100 g/mol) in each tablet. Stomach acid is essentially a hydrochloric acid solution. Is so much calcium carbonate really needed to neutralize stomach acid? Calculate the volume of stomach acid with a pH of 1.0 that one of these tablets could neutralize and compare that value with the normal volume of stomach fluid, which usually is about 100 mL. One tablet can neutralize ________ml of stomach acid at a pH of 1.0. a) 75 b) 150 c) 250 d) 15 e) 1.5

Explanation / Answer

2HCl + CaCO3 ----------> CaCl2 + H2CO3

pH of 1.0 equals a Concentration of 0.10 mol/L

0.75 g of CaCO3 = 0.75 g / 100.08g/mol = 0.007494 mol

moles of HCl needed therefore is 0.007494 x 2 (mol ratio from equation) = 0.014988 moles

Vol of HCl is

moles of HCl needed / Concentration

0.014988 mol / 0.10 mol/L = 0.14988 L or 150 mL

Answer is B

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