Question

How many mL of .715 M HCI is required to neutralize 1.25grams of sodium carbonate? (Producing carbonic acid)

Answer 1

Actually it produces H2O and CO2 although you might argue that it produces H2CO3 a femtosecond before it breaks down to H2O and CO2.

Na2CO3 + 2HCl ==> 2NaCl + H2O + CO2
mols Na2CO3 = 1.25/molar mass Na2CO3.
mols HCl = twice that (look at the coefficients in the balanced equation).
M HCl = mols HCl/L HCl. You know mols and M, solve for L and convert to mL.