Give me some responses to the questions below and I'll give you some extra credit.

SID#:

Laboratory Section: 1 2 3 4 5 6

1. What does the term exothermic mean to you? In your brief description, use words like system, surrounding, reaction, heat, temperature, reactants, products. Note you do not have to use all those words, and you can use others.

Exothermic is the term used to describe heat flow from a system (usually a reaction or phase change) to the surroundings. Heat flows from a region of high temperature to a region of low temperature. So the for an exothermic process the system is at a higher temperature compared to the surroundings. An exothermic reaction has a H^o that is negative. In a chemical reaction the heat term appears on the product's side of the equation;

A + B ---> C + heat

2. What does the term endothermic mean to you? In your brief description, use words like system, surrounding, reaction, heat, temperature, reactants, products. Note you do not have to use all those words, and you can use others.

Endothermic is the term used to describe heat flow from the surrounding into the system. Heat flows from a region of high temperature to a region of low temperature. So the for an endothermic process the system is at a lower temperature compared to the surroundings. An endothermic reaction has a H^o that is positve. In a chemical reaction the heat term appears on the reactant's side of the equation;

heat + C ---> A + B

3. Indicate for each change whether it is endothermic or exothermic. If you do not know say CNA. Be sure to indicate each reaction with its letter.

a. H₂O(l) ----> H₂O(s) Exothermic

b. CO₂(s) ----> CO₂(g) Endothermic

c. 2Na(s) + 2H₂O(l) ----> 2NaOH(aq) + H₂(g) Exothermic

d. 2H₂(g) + O₂(g) ----> 2H₂O(g) Exothermic

I would expect you to be able to predict the change in enthalpy (exothermic or endothermic) for a), b) and d). c) is the difficult one if you have not seen that reaction. Check out the lecture notes for Wednesday's lecture (1/16/02) for more information about general trends we see in particular classes of reactions, and physical changes.

4. Consider the following two reactions. If we had two containers, one holding methane and oxygen, the other holding carbon dioxide and water, in which container is there a greater liklihood of a reaction? Provide a brief explanation if you can.

CH₄(g) + 3O₂(g) ----> CO₂(g) + 2H₂O(l) Spontaneous

CO₂(g) + 2H₂O(l) ----> CH₄(g) + 3O₂(g) Nonspontaneous

Based on experience the reaction between methane and oxygen will occur, and the reaction between carbon dioxide and water will not occur.

5. Can you specify the most likely sequence of the four images?

image #1	image #2
image #3	image #4

Image #4 : Image #1 : Image #3 : Image #2 represents the path we would expect to observe. In Image #4 a solution is added to the solution in the beaker that produces a yellow precipitate. The reaction that is occuring is

Hg²⁺(aq) + 2I^-(aq) ---> HgI₂(s)

More solution is added in Image #1 producing more precipitate. In Images #3 and #2 the precipitate disperses through the solution.

6. If I flipped a coin 20 time, what is the most likely number of heads and tails?

The most probable outcome would be ten heads and ten tails. That arrangement is the most likely to occur.

7. Given the figure below showing 20 gas particles in constant random motion (the image is static, but use your imagination) at time t = 0. If the small red door is open describe what you believe the container would look like after a reasonable period of time.

After the door is opened we would expect there to be 10 particles on both side of the partially open barrier. This is the most probable arrangement, the arrangement with the highest entropy, the arrangement with the greatest disorder.

8. Is there anything about the questions that you feel you do not understand? List your concerns/questions.