Friday, February 4

Class began with a review of Chris's blog from Tuesday. Then, Mr. Henderson announced that, as a result of the snow days, the test was pushed back to Monday. He also mentioned that lab notebooks will also be turned in on test day. Mr. H then provided us with suggestions on how to study. He reminded us of all the study materials we have available; such as the Moodle Review, Delicious bookmarks, unit packet, WebAssigns, and the textbook.
For a review, we did some problems in the packet. We started on page 22 with #9: For the enthalpy (delta H) of the reaction, the products are added and then the reactants are subtracted. When plugging in the standard entropy for just an element, it will always be zero. So for problem 9, the enthalpy should look like 2(o)+1(o)-2(-286)=572KJ. For the entropy (delta S), it should be 2(131)=1(205)-2(70)=372J/K. After finding this, the answer needs to be converted to KJ, so it should be .372. The next part of the problem is to find the temperature range using the equation G=H-T(S). The equation should be 0=572-T(.327) and the final answer should be 1749K and any temperature greater than that is spontaneous.
We then went to page 11 and did problem #1 to practice Hess's Law. The final answer for this problem was -221. To get this, the first equation was multiplied by 2 and the second was flipped.
Next, we did another Hess's Law problem. This one was slightly more difficult. The first equation was multiplied by 2, and the second and third equations were flipped. The final answer was -168.6KJ.
We then finished the Hess's Law Lab. The procedure was to first find Q, using the equation Q=mCT, then to find the moles, and lastly to find the enthalpy by dividing those results.