1.3188g of antacid is weighed and mixed with 75.00 mL of excess 0.1746 M HCl. The excess wcid required 27.20 mL of 0.09767 M NaOH for back titration. Calculate the amount of CaCO3 in the tablet.

The amount of CaCO₃ in the tablet : 0.5219 g

Reaction

1. CaCO₃(in antacid) + 2HCl⇒ CaCl₂+H₂CO₃

2. Titration ⇒ HCl+NaOH⇒NaCl+H₂O

For titration :

M₁V₁.n₁=M₂V₂n₂(n=acid/base valence⇒NaOH/HCl=1)

mol HCl=mol NaOH = excess HCl

mol HCl

Moles of HCl used (reacted with CaCO₃) :

initial HCl - excess HCl =

From reaction 1 :

mol HCl : mol CaCO₃ = 2 : 1

mass of CaCO₃ :

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the answer is b   just took the test