9/30/14 fer-lizer at right is rich in nitrogen as indicated by the “21” as 1. The the first number on the package. This means the fer-lizer is 21% by mass nitrogen. As the package says, this fer-lizer is a mixture of ammonium sulfate and urea. (a)  Determine the mass percent of nitrogen in ammonium sulfate. (b)  Determine the mass percent of nitrogen in urea. (c)  Determine the mass percent of ammonium sulfate in this bag of fer-lizer. (Hint: the 21% is a weighted average of the contribu-ons from each solid). urea class of compounds containing just boron and hydrogen are known collec-vely as 2. The boranes (B H ). A 100 mg sample of an unknown borane was analyzed in order to x y
determine its molecular formula. Complete combus-on of this borane produced 110 mg of water and an unspecified amount of B2O3. A separate experiment determined the molecular weight of the borane to be 123 g/mol. (a) Calculate the moles of water produced from the borane sample. (b) Calculate the mass of hydrogen in the original borane sample. (c) Calculate the grams and moles of boron in the 100 mg sample. (d) Determine the molecular formula of this borane. 1 9/30/14 elements X and Y form a compound that is 40% X and 60% Y by mass. The 3. The atomic mas of X is twice that of Y. Determine the empirical formula of the compound. 4. Xenon hexafluoride reacts vigorously with water according to the following chemical reac-on. XeF6 + 3H2O à XeO3 + 6HF Assume that 100 mg each of xenon hexafluoride and water are allowed to react. Show clear work in determining the maximum theore-cal yield (in grams) of hydrogen fluoride that could be made from the above amount of reagents. 2 9/30/14 lead(II) nitrate decomposes at 400 C to yield nitrogen dioxide, lead(II) oxide, 5. Anhydrous and oxygen gas. o
(a)  Provide a balanced chemical reac-on summarizing this process. (b)  Calculate the kilograms of nitrogen dioxide that can be produced from the decomposi-on of 1 metric ton of lead(II) nitrate. student used a standardized 0.205 M NaOH solu-on to determine the mass 6. A percent of citric acid (H C H O ) in a mixture of citric acid and inert potassium chloride. 3 6 5 7
The per-nent reac-on is H3C6H5O7(aq) + 3NaOH(aq) à Na3C6H5O7(aq) + 3H2O(l) A 0.458 g sample of the mixture required 17.45 mL of the standardized base to completely react with all of the citric acid. Determine the mass percent of citric in this sample. 3 9/30/14 DEF (diesel exhaust fluid) is sold at all gas sta-ons and is 7. Blue now required for use in all diesel engines made ader 2013. The fluid is an aqueous solu-on of urea that is injected into the exhaust stream as needed. The urea reacts with nitrogen oxides and reverts them to environmentally friendly nitrogen gas according to the following unbalanced reac-on: CH4N2O + NO à N2 + H2O + CO2 (a)  Balance the reac-on above. (b)  The Blue DEF solu-on is 33 % (w/w) urea. The solu-on has a density of 1.09 g/mL. Determine the molarity of urea in this solu-on. 4