he Kjeldahl analysis is used to determine the protein content of foods. The food analyzed is heated with sulfuric acid in the presence of a catalyst. The carbon in the protein is converted to carbon dioxide, the hydrogen to water, and the nitrogen to ammonium sulfate. The mixture is then treated with concentrated NaOH(aq) and heated to drive off NH3(g). The NH3(g) is neutralized by an excess standardized acid, and the acid present after the neutralization is titrated with a standardized base. From the titration data and the known mass of the sample, the percentage of N can be calculated. Based on the fact that the average percentage of nitrogen in most plant and animal protein is 16.0%, the percentage of protein is obtained by multiplying the percentage of N by the factor (100/16) = 6.25. Before performing a Kjeldahl analysis, you decide to standardize (i.e., determine the concentration of) the acid to be used in your titration and determine the molarity of your aqueous sulfuric acid to be 0.2496 M. A 2.600-g sample of meat is subjected to Kjeldahl analysis. The liberated NH3(g) is absorbed by adding 50.00 mL of the standardized acid, which is more than enough. This combination produces ammonium sulfate. The excess acid requires 19.90 mL of 0.5510 M aqueous sodium hydroxide for its complete neutralization. What is the percentage of protein in the meat?
The Kjeldahl analysis is used to determine the protein content of foods. The food analyzed is heated with sulfuric acid in the presence of a catalyst. The carbon in the protein is converted to carbon dioxide, the hydrogen to water, and the nitrogen to ammonium sulfate. The mixture is then treated with concentrated NaOH(aq) and heated to drive off NH3(g). The NH3(g) is neutralized by an excess standardized acid, and the acid present after the neutralization is titrated with a standardized base. From the titration data and the known mass of the sample, the percentage of N can be calculated. Based on the fact that the average percentage of nitrogen in most plant and animal protein is 16.0%, the percentage of protein is obtained by multiplying the percentage of N by the factor (100/16) = 6.25.
Before performing a Kjeldahl analysis, you decide to standardize (i.e., determine the concentration of) the acid to be used in your titration and determine the molarity of your aqueous sulfuric acid to be 0.2496 M. A 2.600-g sample of meat is subjected to Kjeldahl analysis. The liberated NH3(g) is absorbed by adding 50.00 mL of the standardized acid, which is more than enough. This combination produces ammonium sulfate. The excess acid requires 19.90 mL of 0.5510 M aqueous sodium hydroxide for its complete neutralization. What is the percentage of protein in the meat?
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