Homework2

# Homework2 - and 0.5 kg of ice cubes to take it to a state...

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Astrobiology Homework #2 (and also a good set of practice problems for the midterm!) Main topic: Chemistry and biochemistry. 1. Suppose you are observing a chemical reaction in the laboratory and measure the rate at which the products are formed at three different temperatures. (Just a reminder: most reactions are multi-step processes, so when you measure the formation rate of products, you really are measuring the rate of the slowest step (rate-limiting step) of the many involved in the reaction mechanism.) Temperature (K) Rate Constant (Mole/sec) 573 2.91 x 10 -6 673 8.38 x 10 -4 773 7.65 x 10 -2 a) Make a simple x,y-plot of rate constant vs. temperature. (Warning: it will look funny!) b) Now, draw an Arrhenius plot, i.e. one that shows a linear relationship between some function of the rate constant and some function of temperature. b) What is the activation energy for the overall reaction? c) What do you expect the rate to be at 600 o C? 2. Let’s return to thermodynamics. a) Calculate how much heat needs to be added to a sealed pot containing 0.5 kg of water
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Unformatted text preview: and 0.5 kg of ice cubes to take it to a state where all of the content vaporize. b) Now calculate how much more energy you would need to add to completely dissociate the water molecules into O and H atoms. This happens in a two-step process. First, the H 2 O becomes OH and H. Then the OH radicals break apart. You will need to look up how strong the OH-H bond is, and how strong the O-H bond is. c) Go c) compare the energy required in each process. 3. The image on the next page shows the molecular structure of coal. The carbon atoms making up the ring structures are not labeled, but they really are there. I have circled several bonds in this structure. Knowing what you now know about chemistry, compare the strengths of the bonds (labeled bonds a, b, c, d, and e). Give a brief statement regarding the relative strengths of each of the bonds: compare a-b, a-c, a-d, a-e, b-c, b-d, b-e, c-d, and d-e....
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## This note was uploaded on 09/08/2010 for the course ASTR 155 at San Jose State.

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