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CH 14 Things to Know
Chemistry Things to Know for Chapter 14
| Question | Answer |
|---|---|
| (S) a measure of how spread out or how dispersed the system's energy is can also be considered to be a measure of molecular disorder. | Entropy |
| For a substance, which phases will have the highest to lowest entropy? | Gas, Liquids, Solids. (gases are more dispersed so highest entropy) |
| Substances with a higher ____ ____ will have a ____ entropy. | Molar mass, higher |
| How does raising the temperature affect entropy? | Substances expand when heated, so therefore the volume becomes larger thus more dispersed than before. |
| Entropy will increase in a sample when: (4) | 1. is heated. 2. occupies a larger volume. 3. mixes with another substance. 4. When it melts, vaporizes, or sublimes (these are all endothermic reactions) |
| Entropy will decrease in a sample when: (4) | 1. is cooled. 2. occupies a smaller volume. 3. separated from a substance it was previously mixed with. 5. when it freezes, condensates, or depositions (these are exothermic reactions) |
| If deltaN Gas=0 then the Entropy for this reaction is equal to | 0 |
| If deltaN Gas is negative then the Entropy for this reaction will be | Negative |
| If deltaN Gas is positive then the Entropy for this reaction will be | Positive |
| When determining what deltaN Gas is for a reaction, what do you look at? | Moles of gases on products and reactants, |
| What is the equation used to determine the deltaN Gas of a reaction? | moles of gas products-moles of gas reactants |
| If you are trying to determine the change in Standard Entropy, what is the equation? | Sum(moles of products*standard entropy of products)- Sum(moles of reactants*standard entropy of reactants) |
| What is the difference between the "system" and the "surrounding"? | The system is the *thing* you are studying whereas the surrounding is everything else. |
| "The entropy of a perfect crystalline substance is zero at absolute zero." -____ Law of Thermodynamics | Third |
| Exothermic (-deltaH) processes are typically referred to as ____ processes and are usually _____. | Downhill, spontaneous |
| Endothermic (+deltaH) processes are typically referred to as ____ processes and are usually _____. | Uphill, nonspontaneous |
| What is the difference between a spontaneous reaction and a non spontaneous reaction? | A spontaneous reaction occurs without the aid of outside forces whereas a non spontaneous reaction depends on an outside force to occur. |
| What is the equation for calculating deltaS of the universe? | deltaS System + deltaS surroundings |
| When an ice cube melts, what is the heat flow? Also, what kind of process is this? | Heat Flow: Surroundings-->System (ice cube (system) is taking heat in from the surroundings to melt itself). This is an endothermic process. |
| When you cool a hot cup of water, what is the heat flow? Also, what kind of process is this? | Heat Flow: System-->Surroundings (hot water (sytem) is releasing heat (energy) into the air (surroundings) to cool itself). This is an exothermic process. |
| For an endothermic reaction, the ___ value increases while the _____ value decreases. | System, Surroundings |
| For an exothermic reaction, the ___ value increases while the ____ value decreases. | Surroundings, System |
| If given only system values, how can you calculate for deltaS Surroundings (equation)? | -deltaH/T (REMEMBER: system values NEVER have a subscript!) |
| If given surroundings values, how can you calculate for deltaS Surroundings (equation)? | deltaH_surroundings_/T |
| "The total entropy of the universe continuously increases."- __ Law of Thermodynamics | Second |
| deltaS Universe is ALWAYS ____ | Positive |
| When a process is at equilibrium, deltaS Universe will equal | 0 |
| (G) can be used to express spontaneity. | Gibbs Free Energy |
| What is the equation for Gibbs Free Energy? | deltaG=deltaH-T*deltaS |
| When you have a -deltaG, then the reaction is _____. | Spontaneous. |
| When you have a +deltaG, then the reaction is _____. | Non Spontaneous |
| When you have a deltaG=0, then the reaction is ____. | At equilibrium. |
| When you have -deltaH and a -deltaS, the reaction is _____ at ____ ____. | Spontaneous, at Low Temp. (Think about if you are trying to freeze water, this reaction will ONLY happen naturally at a low temp aka below 0 degrees Celsius) |
| When you have a +deltaH and a +deltaS, the reaction is ____ at ____ ____. | Spontaneous, at High Temp. (Think about if you are trying to melt ice, this reaction will ONLY happen naturally at a high temp aka above 0 degrees Celsius) |
| When you have a -deltaH and a +deltaS, the reaction is ____ | Spontaneous |
| When you have a +deltaH and a -deltaS, the reaction is____ | Non Spontaneous |
| Favored direction for a reaction will change when deltaG=___ | 0 |
| What is Standard deltaG_f_ | Gibbs Formation Energies |
| How to find standard deltaG for a reaction? (equation) | Sum(moles of products*deltaG_f_ of products)-Sum(moles of reactants*deltaG_f_ of reactants) |
| When you have an element in its most stable allotrope, what is the Standard deltaG_f_ for that element? | 0 |
| For something to be considered in a standard state it has to be ____ , ____, and ____. | Pure, unmixed, and 1 M solution. |
| There are many biological reactions that are non spontaneous even though they have a +deltaG, but when paired with a _____ ____ they become possible. Name an example. | Spontaneous reaction, ATP and ADP |
Created by:
jrr409