Questions on Stoichiometry

CHEM 14
Problem Set 2

Deadline of submission: MHE2 – Feb 7; TFC – Feb 8

SOLVE ALL PROBLEMS. SHOW YOUR SOLUTIONS CLEARLY.
1. Arginine is a semi-essential amino acid that is used to form nitric oxide which in turn plays an important role in the nervous as well as cardiovascular system. It contains C, H, N and O. Combustion of a 0.75 g pure sample which contains 2.591 x 1021 molecules of the amino acid produced 0.03015 mols of water and 578.59 mL of CO2 at STP. The same sample contains 5.181 x 1021 oxygen atoms. Determine the empirical and molecular formula of the compound.
2. A. Copper can be produced from the reaction of aluminum and excess copper(II) sulfate: Al(s) + CuSO4(aq)  Al2(SO4)3(aq) + Cu(s)
B. How many moles of aluminum is necessary to produce 4.50 g of Cu if the reaction is 91% complete?

3. A. How many grams of disulfur dichloride is produced from the reaction between 20 g of sulfur and 80 g of chlorine?
B. How much of the excess reactant remained? (The reaction is 100% complete.)
S8(s) + Cl2(g) → S2Cl2(g)

4. Nitroglycerin, an organic explosive, decomposes according to the following equation:
4 C3H5(NO3)3(s)  12 CO2 (g) + 10 H2O (g) + 6 N2 (g) + O2(g)
A 500 g sample containing nitroglycerin was allowed to decompose.
A. If the decomposition yielded 67.8 g of H2O what is the percent purity of the sample?
B. How many liters of CO2, N2, and O2 were produced from this decomposition?

5. Cyclopropane mixed in the proper ratio with oxygen gas can be used as an anesthetic.
A. At 755 mm Hg and 25C, cyclopropane has a density of 1.71 g/L. What is its molar mass?
B. If 15 g of the anesthesia mixture which generally consists of 30% oxygen, is placed in a 40-L steel cylinder at 25C, what is the partial pressure of cyclopropane?
C. What is the total pressure in the cylinder if the temperature dropped to 20C?