Chemistry 104 Exam 01 Spring 2008–09

Answer concisely but clearly any five (5) of the following during the 70-minute period. Show intermediate steps where appropriate. You may have access to Chapters 1 to 3 for reference material, but not the hints/answer section at the back.

1.   An “extreme beer” movement has occurred in Britain. While a traditional pub offering is 4% to 5% ethanol (by volume), the new products range upward to 10% in ethanol concentration, with BrewDog on the verge of launching Divine Rebel at 12.5%. The governmental health guidance for men is up to 40 mL of ethanol per day averaged over a week. (a) How many pints (568 mL volume) of 4% alcoholic beverage consumed during one week would fall within that guidance limit? (b) How many 330 mL bottles of Divine Rebel consumed during one week will fall within the same guidance limit? (c) Given Mr = 46.0 and density = 0.789 g mL-1 for ethanol, what is the concentration of ethanol (mol L-1) in Divine Rebel?
2.   A weed killer sold in a concentrated liquid form contains 2,4-D (Mr = 221) and other active ingredients. Information from the package label indicates that the concentrated liquid contains 26 g L-1 of 2,4-D. Directions for use specify dilution by a factor of 64 before use. Then the diluted solution should be applied uniformly at 100 mL per m2, say upon a golf course for selective killing of broadleaf plants while leaving grass largely unaffected. How many 2,4-D molecules would fall upon just one cloverleaf of area 1.0 cm2? The Avogadro constant is 6.0 x 1023 mol-1.
3.   For each of the situations (a) amount-of-substance concentration of a glucose solution for IV infusion, (b) cardiac output, (c) interior volume of a white blood cell, (d) number of legs on a millipede, (e) pressure applied to a puncture wound to promote closure of blood vessels, (f) rate of clearance in the liver of a toxin circulating in the blood, (g) speed of nerve conduction, choose the most appropriate SI-related units of measure from the following list: (A) a dimensionless quantity, (B) m s-1, (C) mL s-1, (D) mmol mL-1, (E) mol dm-2, (F) µm3, (G) µmol L-1 s-1, (H) N m-2.
4.   Ordinary ether has the molecular composition C4H10O, but not uniquely so. Sketch the structures, i.e., the atomic connectivity, of the isomers of (a) each of the three ethers and (b) each of the four alcohols sharing this particular composition and conforming to standard chemical valencies. Assume local tetrahedral geometry at each carbon atom. Identify which one structure out of the seven can exist in mirror image forms.
5.   Bacillus anthracis has brought about human suffering since ages past, as deduced from the fifth and sixth plagues of Egypt (described in Exodus), the writings of Virgil in 25 BC, and the Black Bane of medieval times. This relatively large rod-shaped bacterium has a diameter of 1.1 µm and an overall length of 4.0 µm. Approximate the shape at the ends as two hemispheres. (a) What is the total interior volume? (b) What is the total surface area? (c) What is the surface to volume ratio?
6.   Begin from the definition of pressure and deduce to what depth a whale would have to dive in the sea in order for the pressure to become ten times the atmospheric pressure at the surface, which is 101 kPa. Also, approximating a whale lung as a sphere and assuming a quick dive using up very little air, express the diameter of that lung at this depth as a fraction of its diameter at the surface. The acceleration of gravity is 9.8 m s-2 and sea water has a density of 1024 kg m-3.
7.   A bacterial cell culture is diluted serially as follows: 0.1 mL of the initial culture plus 9.9 mL of a diluent => Sample 1; 0.1 mL of Sample 1 plus 9.9 mL of diluent => Sample 2; 0.5 mL of Sample 2 plus 9.5 mL of diluent => Sample 3. Assume that there is no shrinkage or expansion of volume when these solutions are mixed. After plating 100 µL of Sample 3 on each of several plates of nutrient medium, an average of 80 bacterial colonies per plate is found. Each colony grows from one bacteria ancestor. What is the concentration in cells per milliliter of the initial bacterial culture?

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