Quantitative Analysis Course - Titration Problem

[Raihn]

A typical protein contains 16.2% nitrogen (14.00674 mg/mmol). A 0.500 mL aliquote of protein solution was digested, and the liberated NH3 was distilled into 10.00mL of 0.02140 M HCL. The unreacted HCl required 3.26mL of 0.0198 M NaOH for complete titration. Find the concentration of protein (mg protein/ mL) in the original sample.

I'm not entirely sure on where to start first. Should I convert the HCl and NaOH into moles? Or? Not entirely sure of what to do first. If someone can give me a hint, most appreciated.

If converting them to moles is the first step, where do I go from there to find the concentration of the protein?

Thank you in advanced.

[Ygggdrasil]

The first step would be to write out balanced equations for the relevant chemical reactions that are going on during the process. That should help you understand how the different measurements relate to each other and how you can use them to derive the final result.

[symbolipoint]

Definitely the analysis is complicated but it uses a chain of distinct processes. Try working it backwards. Start with the uncreacted moles of HCl.

[Borek]

http://www.titrations.info/back-titration