[Psionex]

Please help me with these questions, thank you very much! I've tried for so long but am still as lost and blur as ever!!!

1. The purity of a pharmaceutical preparation of sulphanilamide, C6H8N2O2S (m.w. 172.20), can be determined by oxidizing the sulphur to SO2 and bubbling the SO2 through H2O¬2 to produce H2SO4. The acid is then titrated with a standard solution of NaOH to the bromothymol end point, where both of the sulphuric acid protons have been neutralized. Calculate the purity of the preparation, given that a 0.5136 g sample required 46.75 mL of 0.1251 M NaOH.

2. The protein in a 1.2846 g sample of an oat cereal is determined by Kjeldahl procedure for organic nitrogen. After digesting the sample of oat cereal, the organic nitrogen is oxidized to NH4+, converted to NH3 with NaOH and deionized into a collection flask containing 50.00 mL of 0.09552 M HCl. The excess HCl is then back titrated using 37.85 mL of 0.05992 M NaOH. Given that the protein in grains averages 17.54% w/w N, report the % w/w protein in the sample of cereal.

[Borek]

Start with relevant reaction equations. It all boils down to simple stoichiometry.