Today we entered class with two sheets waiting to be picked up on the front desk. Two sheets titled Energy and Reactions 1. After grabbing those two sheets and taking a seat, Mr. Tucker had gone around and stamped the homework from the night before. Once that was done, he had gone over some problems from the night before. Here are some answers that we went over class (they might vary):
CALCULATIONS
1. Mass of original water
101.66 g.
2. Mass of water from melted ice (subtract mass of ice in water from the original water)
17.71 g.
3. Change in temperature of water
13 degrees Celsius
4. Amount of heat lost by original
5,524.2 J.
5. Heat Fusion for the Ice
311.914 J/g
QUESTIONS
1.Is the process of the ice melting endothermic or exothermic?
Endothermic. Heat is traveling on/into the ice.
2.Is the process of the ice freezing endothermic or exothermic?
Exothermic. The energy is traveling out of the ice.
SKIP #3
We then continued on to the worksheets we had picked up in class. We had done #1 a & b in class. These are the answers we got as a class for that sheet:
1. CH4 + 2o2 -> CO2 +2H2O
a. 4.00 g of Methane (CH4) is allowed to burn according to the reaction above. The energy released by the reaction is used to head 800 grams of water from 15.0 degrees Celsius to 81 degrees Celsius.
-Find the energy released by the reaction in kJ.
800g x 4.18J/gºC x 66.4ºC = (app.) 222 kJ
-Find the moles of CH4 burned.
4.0g CH4 x 1mol/16.04g = .249 mol CH4
-Find Delta H in kJ/mol (including the sign) for the reaction above.
222kJ/.249 mols = 892 kj/mols
** remember delta H (which is heat associated with reaction)/ 892 kj/mol
b. In another experiment 1.55 g of CH4 is burned. How much energy would be released?
1.55 g CH4 x 1 mol CH4/16.04 g CH4 x 892 kJ/1 mol CH4 = 86.197 KJ -> 86.2 kJ
By the time we had gone over these problems in class, we were instructed to finish the rest of the two sheets for homework!
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