Stoichiometry ,gas problem

[Big V]

the question is:
Sodium Hydrogen carbonate (baking soda) is reacted with excess acetic acid (vinegar) with a concentration of 0.500mol/L in an Erlenmeyer flsk. The proucts are sodium acetate, water and carbon dioxide gas. The gas produced is collected in a balloon attached to the flask, tied off with a string and then weighed. Using the information from the data below, predict the mas of carbon dioxide produced and the percent error in the experiment.

other data given :
Mass of... balloon (g) 13.5
string (g) 1.2
balloon, string, gas (g) 16.5
solute (g) 5.0

the part i don't get is which number do i use to find moles so that later i can use those moles to find the mass . like is the mass of solute (5.0) , the mass of sodium hydrogen carbonate.
please help sorry if I'm confussing

 

[symbolipoint]

Determine these two pieces of information first:

Write the balanced reaction.
Compute how much gas is in the baloon.

You said that the acetic acid is in excess, so the limiting reactant must be the sodium bicarbonate.

 

[Big V]

balanced reaction :
(this is how i would set up my data)
CH3COOH + NaHCO3 → CH3COONa + H2O + CO2
C= 0.500mol/l________________________ m=?

Gas in Balloon:
16.5-1.2=15.3
-13.5= 1.8
gas =1.8g