Energy Entropy Flashcards

Question

What is entropy? How do you calculate it?

Answer 1

- It is measure of the dispersal of energy in a system which is greater, the more disorder a system 1. We can think of entropy as a measure of randomness and chaos 2. Every chemical reaction has an associated entropy change 3. DeltaS = products - reactants

Answer 2

1. If a system becomes more random, energy can be spread out more and deltaS is positive (more disorder) (liquid to gas) 2. If a system changes to become less random, energy becomes more concentrated and deltaS is negative (less disorder) (liquid to solid) 3. The greater the entropy, the greater the dispersal of energy and the greater the disorder

Answer 3

1. Reactions only happen when the products have a lower overall energy than the reactions 2. Overall energy is represented by the Gibbs equations and has two contributions: - Enthalpy change - The entropy change at the temperature of the reaction - DeltaG = DeltaH -TDeltaS 3. If DeltaG < 0 the reaction is said to b energetically feasibly and will occur at the given temperature

Answer 4

1. Whether a reaction is feasible: -Feasible reaction are spontaneous at T when G<0 -Feasible reactions have a lower overall energy in their products 2. Why endothermic reactions can take place at room temperature -If DeltaH is positive, DeltaG is less than 0 when TDeltaS>DeltaH and Delta S is positive 3. What the minima temperature for reaction feasibility might be T > DelatH / DeltaS

Answer 5

- Some reactions have a negative deltaG bur do not seem to take place 1. Diamond into graphite 2. Decomposition of hydrogen peroxide into water and oxygen

Answer 6

"Feasibility" just means that a reaction is theoretically possible at that temperature. It does not tell us anything about the speed of the reaction. Kinetics is just as important as thermodynamics when considering reaction. Some reactions are feasible, but infinitely slow due to a very large activation energy barrier

Answer 7

1. Entropy increases during changes in state that give a more random arrangement of particles: solid->liquid->gas 2. So when any substance changes state from a solid to liquid to gas, its entropy increases - Melting and boiling increase the randomness of particles - Energy is spread out more and DeltaS is positive

Answer 8

1. Reactions that produce gases result in an increase in entropy, for example calcium carbonate reaction with hydrochloric acid: - Production of a gas increases the disorder of particles - Energy is spread out more and deltaS is positive 2. You can precept the sign of the entropy change for reaction where the reactant and products have different numbers of gas molecules, for example in the reaction of nitrogen and hydrogen gases to produce ammonia results in a decreases in the number of gas molecules - There is a decrease in the randomness of particles - The energy is spread out less and DeltaS is negative

Answer 9

Electrolysis of water

Answer 10

As temperature increase TdelatS becomes more negative and becomes too large in magnitude so that it outweighs deltaH and eventually deltaH-TdeltaS becomes positive

Answer 11

1. Enthalpy of hydration for F- more negative/exothermic than for Cl- as F- has a smaller size than Cl- 2. F- so smaller sized ion so greater attraction to H2O

Answer 12

1. K+ ionic radius is smaller so greater charge density 2. Lattice enthalpy of KF is more negative than RbF 3. DelatHhydration of K+ is more negative than for Rb+ (K+ has greater attraction for H2O) 4. Enthalpy change of solution affected more by lattice enthalpy than by hydration enthalpy

Answer 13

1. During dissolving entropy/ disorder is increased | 2. TdeltaS is greater than deltaH so deltaH-TDeltaS is negative

Energy Entropy Flashcards

(37 cards)