Need help on chemistry: molarity, purity problem

need help on this problem:

An impure sample of solid Na2CO3 is allowed to react with 0.1755 M HCl.
Na2CO3 + 2HCl ---> 2NaCl + CO2 + H2O
A 0.2337-g sample of sodium carbonate requires 15.55 mL of HCl solution. What is the purity of the sodium carbonate?

Here's what i got:
0.2237 g Na2CO3 x (1 mol Na2CO3/ 105.99 g Na2CO3) x (2 mol HCl/ 1 mol Na2CO3) = .004221 mol HCl

.004221 mol HCl/ 0.1555 L= .2714 M HCl ---> (.1755 M/ .2714 M) x 100 = 64.66%

Is this correct?
Thanx for checking.

0.1755 M HCl x 0.01555 L=0.00273 moles HCl
1 mole HCl reacts with 2 moles Na2CO3
0.00273 x 1/2 x 105.99 g/mole Na2CO3=0.1447 g Na2CO3 required
0.1447 g Na2CO3 req./0.2337 g x 100= 61.9 % Na2CO3