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chemistry 17
chpt 17
| Question | Answer |
|---|---|
| Enthalpy reaction | the quantity of energy transferred as heat during a chemical reaction. |
| enthalpy formation | enthalpy change that occurs when one mole of a compound is formed from its elements in their standard state at 25 degrees and 1 atm. |
| enthalpy combustion | the energy released as heat by the complete combustion of a specific amount of a substance at a constant pressure or constant volume. |
| entropy | measure of the randomness or disorder of a system |
| entropy decrease | decrease is when the particles are at low random, Ex freezing water you are converting it froma liquid to a solid so therefore forcing the particles to be more at random. |
| entropy increase | EX. paper burning its more at random so therefore an increase in entropy because you are converting the solid paper to another state of matter. |
| thermochemical equations | 2h2+o2-->2h2o+483.6KJ of energy |
| free energy change | delta G, a system that is defined as the difference between the change in enthalpy, delta H, and the product of the kelvin temperature and the entropy change(t Delta s) |
| free energy equation | delta (G)=HR-T(delta S) |
| Reaction 1 | if T and S are both positive the reaction will only occur IF it is at high temperature and the sum is great then HR. |
| Reaction 2 | HR (+) and S (-) and If (G) is positive the reaction will never occur! but if (G) is negative the reaction will occur. |
| Reaction 3 | HR (-) delta S (-) reaction can still take place. |
| Heat of FOrmation | H2+ .5o2-->H2o +241.8 KJ the amount of energy changes that occur when a compound is freed from its elements is an indication that formed when it is a compound. The more energy thats given off when its formed the more stable the compound. |
| hess's Law | the overall enthalpy change in a reaction is equal to the sum of enthalpy changes for the individual steps in the process. |