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# The human body excretes nitrogen in the form of urea, $\mathrm{NH}_{2} \mathrm{CONH}_{2} .$ The key step in its biochemical formation is the reaction of water with arginine to produce urea and ornithine:(a) What is the mass $\%$ of nitrogen in urea, in arginine, and inornithine? (b) How many grams of nitrogen can be excreted asurea when 135.2 $\mathrm{g}$ of ornithine is produced?

## a) fraction(N,urea) $=46,64$ percentfraction(N,arginine) $=31,98$ percentfraction(N,ornithine) $=21,04$ percentb) $\mathrm{m}(\mathrm{N})=28,44 \mathrm{g}$

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Chemical reactions and Stoichiometry

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to calculate the percent nitrogen in the three different compounds given in this reaction. First, we need to have the molecular formulas from structural formula. It's so given the diagrams we can draw, we can write our structural formulas. When we look at the first compound, you see the elements present or kurban hydrogen, nitrogen and oxygen. There are six carbons, 15 hydrogen for a nitrogen and to oxygen's we already have. The formula for Yuria that's been given to us is and each to C O and H two. And finally, for the last compound, we used the picture again to determine the formula. There are five carbons, two nitrogen ins, 13 hydrogen zones and to Oxygen's. Once we have the formulas for each, we can find the molar mass or each. We do that, using our periodic table and adding up the individual molar masses and multiplying by their coefficients. So the first compound has the molar mass of 175.216 grams. Permal second compound Yuria has a Mueller math of 60 0.56 grams per mole, and finally, our last one has a molar mass of 133 0.173 grams per mole. And again, these numbers come from looking up the individual molar masses and multiplying by their sub scripts. Find the percent nitrogen we simply look at the number of nitrogen is in each compound. So for the 1st 1 there are four multiplied by the molar mass of nitrogen and then divide by the total Mueller Mass and multiplied by 100 in the Sequels, 31.98 percent. This one we also have We have to nitrogen, divided by the molar mass times 100 which gives us 46 0.65%. And finally, in our last compound there are two nitrogen divided by the total Moeller mass times 100 or 21 0.4%.

University of Maine

#### Topics

Chemical reactions and Stoichiometry

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