J.R. S. answered 08/15/21
Ph.D. University Professor with 10+ years Tutoring Experience
Look at the balanced equation for the reaction takin place:
CaCO3 + 2HCl ==> CaCl2 + H2O + CO2
(a) moles HCl present = 25 ml x 1 L/1000 ml x 0.75 mol/L = 0.01875 mols HCl
mols CaCO3 needed = 0.01875 mols HCl x 1 molCaCO3 / 2 mol HCl = 0.009375 mols CaCO3
mass CaCO3 needed = 0.009375 mols CaCO3 x 100.1 g CaCO3/ mol = 0.938 g = 0.94 g CaCO3 (2 sig. figs.)
(b) At STP 1 mole of any ideal gas = 22.4 L. Assuming ideal gas behavior..
mols CO2 formed = 0.01875 mols HCl x 1 mol CO2 / 2 mol HCl = 0.009375 mols CO2
0.009375 mols CO2 x 22.4 L / mol = 0.21 L CO2