The purity of a pharmaceutical preparation of sulfanilamide, C6H4N2O2S, can be determined by oxidizing the sulfur to SO2 and bubbling the SO2 through H2O2 to produce H2SO4. The acid is then titrated with standard NaOH. Calculate the purity (%w/w sulfanilamide) given that 1.457 g of the sulfanilamide sample required 20.6 mL of 0.3443 M NaOH. (Note: 1 mol sulfanilamide = 1mol S = 1mol H2SO4)

Question

The purity of a pharmaceutical preparation of sulfanilamide, C6H4N2O2S, can be determined by oxidizing the sulfur to SO2 and bubbling the SO2  through H2O2 to produce H2SO4. The acid is then titrated with standard NaOH. Calculate the  purity (%w/w sulfanilamide)  given  that 1.457 g of the sulfanilamide sample required 20.6 mL of 0.3443 M NaOH. (Note:  1 mol sulfanilamide = 1mol S = 1mol H2SO4)

DrBob222 · Accepted Answer

The titration step is
2NaOH + H2SO4 ==> 2H2O + Na2SO4.

moles NaOH = M x L = ?
Convert to moles H2SO4.
moles NaOH x (1 mol H2SO4/2 mol NaOH) = ?
moles H2SO4 = moles sulfanilamide according to your information.
g sulfanilamide = moles sulf x molar mass sulf
%purity = (mass sulf/mass sample)*100 = ?

Charles Appau Mensah · Answer

58.5%