A classical procedure for determining nitrogen in materials is called the Kjedah

Question

A classical procedure for determining nitrogen in materials is called the Kjedahl method. The sample is digested in concentrated sulfuric acid with a reducing agent to convert all nitrogen into ammonia. In the classical procedure, the solution is made basic and the ammonia is evaporated out of the mixture as a gas and trapped in an aqueous solution, where it is titrated with acid. A modern variation on this procedure used coulometric titration to react the ammonia in situ with electrogenerated hypobromite.

Br-1 + 2 OH-1

Explanation / Answer

So far what I have done is: moles HCL = (.500L)(.2000M) = .1000moles moles NH3 = volume * .0742M) = ?? .1000moles - moles NH3 = moles of NH4 grams of nitrogen = (moles of NH4)(14.00g) %nitrogen= grams nitrogen/5.503g *100% Initially there are (0.2M X 0.5L) = 0.1 moles of HCL After the reaction, I am unsure of the volume to use for HCL because of "The unneutralized acid is then determined by titration". Would I not assume the volume has increased? Not knowing how much was required for titration is what is confusing me. If I should assume volume is unchanged then (0.5L * 0.0742M) = 0.0371 moles (0.1 - 0.0371) = 0.0629 moles is the difference. "What happenned to the missing HCl?" - This I am unsure of. This is how I understand where we are now. I calculated the original concentration of HCl to be 0.1 moles, the concentration after titration being 0.0371 moles. (0.1 - 0.0371) = 0.0629 moles is the difference. grams of nitrogen = (0.0629moles)(14.00g)= 0.8806 g of Nitrogen %nitrogen= 0.8806g/5.503g *100% = 16% of Nitrogen in the sample of protein? For some reason I feel my calculations are missing something ie. the new volume after titration, or something similar. My professor usually tries to trick us, so this would be unlike her to make it doable on the first try

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