The Kjeldahl method is used in agricultural chemistry to determine the percent protein in natural products. The
Question:
The Kjeldahl method is used in agricultural chemistry to determine the percent protein in natural products. The method is based on converting all the protein nitrogen to ammonia and then determining the amount of ammonia by titration. The percent nitrogen in the sample under analysis can be calculated from the quantity of ammonia produced. Interestingly, the majority of protein molecules in living matter contain just about 16% nitrogen. A 1.250 g sample of meat is heated with concentrated sulfuric acid and a catalyst to convert all the nitrogen in the meat to (NH4)2SO4. Then excess NaOH(aq) is added to the mixture, which is heated to expel NH3(g). All the nitrogen from the sample is found in the NH3(g), which is then absorbed in and neutralized by 50.00 mL of dilute H2SO4(aq). The excess H2SO4(aq). requires 32.24 mL of 0.4498 M NaOH for its titration. A separate 25.00 mL sample of the dilute H2SO4(aq) requires 22.24 mL of 0.4498 M NaOH for its titration. What is the percent protein in the meat?
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General Chemistry Principles And Modern Applications
ISBN: 9780132931281
11th Edition
Authors: Ralph Petrucci, Jeffry Madura, F. Herring, Carey Bissonnette