Chem 147 First Midterm Examination 26 April 2007

1) Is carbon better suited that silicon to support complex chemistry, like the chemistry that supports life on Earth? If so, how? If not, why not? (14 pts)

2) How old is the Earth, and how do we know this? (14 pts)

3) On Tuesday of this week (!) astronomers in Europe announced the discovery of an exoplanet (i.e. outside our Solar System) that is only ~5 times the Earth’s mass and orbits close enough to its red dwarf star (at a measly 0.07 AU) that it is likely in the “habitable zone” where the mean temperature is in the liquid range for water. They have also identified a Neptune-sized planet in the same solar system. Do you think this new, smaller planet is likely inhabitable? (10 pts)

4. As we will discuss later in the course a number of large (Jupiter-sized or larger) exoplanets have been found in orbit around stars beyond our Sun. Many of these planets orbit extremely closely to their primary stars, often closer than Mercury orbits the Sun. Can this observation be reconciled with the equilibrium condensation model of the formation of the solar system? If so, how? If not, why not? (12 pts)

5. What is the dominant constituent of the Earth, and what experimental observations support your claim? (12 pts)

6. An unusual property of the carbon-12 nucleus renders the fusion of three ⁴He into ¹²C a relatively efficient process. What is this property? (14 pts)

7. What physical properties render a molecule a gas a greenhouse gas? (12 pts)

8. Why doesn’t Miller-Urey chemistry produce lipids? (10 pts)