|Chemistry 104||Exam 02||Spring 2009–10|
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 5 for reference material, but not the hints/answer section at the back. No collaboration, phone calls, text messaging, etc.
|1.||An adult human has about 1013 cells produced by cell division from a single fertilized egg. (a) Approximately how many generations of cell divisions would be needed to get to the scale of an adult? (b) Human cells divide only about once every 24 hours. If all cells continue to divide at this rate throughout development, how long would it take to get to an adult? (c) Explain whether the result from (b) is in agreement with the actual situation.|
|2.||The chloroplasts in spinach leaves strongly absorb light in a band centered at 430 nm and less strongly absorb in another band centered at 650 nm. If two spinach plants are grown under separate lights, one a green light and the other a blue light, which plant will thrive best? Why?|
|3.||In the Lowry assay for proteins, which is not as rapid to do as the Bradford assay, an absorbance increase at 660 nm is approximately proportional to the amount of protein added to the appropriate reagents. In one experiment calibrated with bovine serum albumin, data posted by Jewett in 2000 imply that the mass-based ε was 0.018 µg-1 cm-1 under the conditions of measurement. (a) What was the actual composition of an unknown protein solution if 10 µL of it produced an absorbance increase of 0.12 when assayed in a 1 cm cuvette under the same conditions? (b) What percentage of the incident light gets through to the detector in this latter experiment?|
|4.||Explain with a few sentences and supporting expressions and/or sketches an appropriate graphical technique by which you could determine the exponent m for a proposed power law relationship between body mass and wing area for birds, i.e., (wing area) = constant x (body mass)m. Assume that you have data for 20 species of birds ranging in size from the Cuban bee hummingbird (Mellisuga helenae) through to the condor (Gymnogyps Californianus).|
|5.||The government regulatory level is 1.0 mg/L for the toxic element cadmium in the environment. Replicate samples from a waste stream were measured as containing 2.0, 1.5, 0.9, 0.8, 1.3, 1.1, 0.5, 2.4, and 1.8 mg/L of cadmium in the water. (a) Calculate the mean, the standard deviation, and the 95% margin of uncertainty. (b) Explain whether regulatory action called for at the 95% level of confidence.|
|6.||The calcium content (units of mg/L) of a person’s urine was determined on two different days: m = 238, s = 8, n = 4; m = 255, s = 10, n = 5. Find out whether the calcium concentration has increased at the 95% confidence level. Explain the calculations.|
|7.||Data adapted out of a larger collection presented by Galton in 1886 showed that the heights of n = 45 adult children whose tall parents had a mean height of 72.5 inches were as follows (rounded to the nearest inch): 1 at 65 inches, 3 at 66, 4 at 67, 5 at 68, 5 at 69, 10 at 70, 4 at 71, 9 at 72, 2 at 73, and 2 at 74. (a) Sketch the frequency histogram. (b) What are the observed quintile locations (to the nearest inch)? (c) On the assumption of normally distributed values, m = 69.8 inches and s = 2.2 inches, what would have been the expected quintile locations (to the nearest 0.1 inch)? (d) Where are the expected locations that encompass 95% of the heights of the children? (e) Explain whether the child whose height is 65 inches is unexpectedly short in stature, with 95% confidence. (f) If you could not discern the difference between a parent and a child by age, could you do so by height, with 95% confidence?|
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