1. Why is it necessary to equalize the pressure(i.e, have the water level the same in each tube) before taking a volume reading?

2. Why is it important to use water that has been pre-saturated with CO2 in the gas burettes?

3.If your antacid sample had been contaminated by moisture, what effect(if any )would you expect this to have on your result

4.Explain why an'antacid is called as such,what is the role of the NAHCO3 or CACO3 in reactions?

If you contact water with a gas at a certain temperature and (partial) pressure, the concentration of the gas in the water will reach an equilibrium ('saturation') according to Henry's law.

Explanation:

This means: if you increase the pressure (e.g. by keeping the vial closed), the CO2 concentration will increase. So it simply depends what concentration you need for your assay: 'CO2-saturated' water at low pressure or 'CO2-saturated' water at high pressure.