J.R. S. answered 05/10/18
Tutor
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Ph.D. in Biochemistry--University Professor--Chemistry Tutor
First, you must write a correctly balanced equation:
2HCl + CaCO3 ==> CaCl2 + H2O + CO2
Moles of CaCO3 present = 0.200 g x 1 mole/100.0 g = 0.002 moles
Moles HCl needed to react = 0.002 moles CaCO3 x 2 moles HCl/mole CaCO3 = 0.004 moles
mls of HCl needed: (0.121 mol/L)(x L) = 0.004 moles
x = 0.0331 mls