What volume of 3.00M HCl in liters is needed to react completely (with nothing left over) with 0.750L of 0.400M Na2CO3?

Answer 1

Na2CO3 + 2 HCl --> CO2 + H2O + 2 NaCl

How many mols of Na2CO3 do we have?
.75* .4 = .3 mols

so we need .6 mols of HCl
We have 3 mols in every liter

.6 mols/ 3 mols/liter = .2 liters