Active Ingredient and gas pressure

[gamergeekgrl]

I have these two questions left to answer in an online TIMED quiz right now, and have no idea how to solve them. I've searched all through my text and notes and can't find anything. ANy help would be really appreciated!

 

In a calibration experiment, a 1.04 millimole sample of Na2CO3 gave 0.82 millimoles of CO2 gas. If a 0.346 g of pure Na2CO3 was reacted with excess acid, what volume of gas will be measured on this apparatus (in Litres at STP)? (Hint: Start by calculating the percent yield)

 

The antacid in question (with an active ingredient of Ca(HCO3)2), upon treatment with excess hydrochloric acid, a 0.433 g sample gives 88.15 mL of CO2 at 25.00oC and 1.000 atm. What percentage of the antacid is active ingredient? Assume a perfect system (i.e. the yield is 100%)