In an experiment an unknown mass of anhydrous sodium carbonate was dissolved in water and the solution made up to 250cm³. 25cm³ of this is neutralised 20cm³ of 0.25M nitric acid. (Na=23.0,C=12.0,O=16.0) calculatea)moles of nitric acid used.b)moles of sodium carbonate in 25cm³ of the solution.c) mass of unknown sodium carbonate level