thermodynamics

Question 1

thermodynamics definition

Answer 1

transformation of energy from one form to another

Question 2

zeroth law

Answer 2

when systems are in thermal equilibrium with one another, their temperatures must be the same

Question 3

first law

Answer 3

energy can’t be created or destroyed

Question 4

three designations for energy flow

Answer 4

system, surroundings, thermodynamic universe

system + surroundings = universe

Question 5

Rules for energy flow

Answer 5

when energy flows into a system from the surroundings, energy of system increases and energy of surroundings decreases

when energy flows out of a system into surroundings, energy of system decreases and energy of surroundings increases

Question 6

enthalpy

Answer 6

measure of the heat energy that is released or absorbed when bonds are broken and formed during a reaction that’s run at constant pressure

Question 7

heat energy (H) when bonds are formed and broken

Answer 7

delta H < 0 when bonds are formed

delta H > 0 when bonds are broken

Question 8

exothermic vs endothermic

Answer 8

exothermic - more energy released in the making of products bonds than was put in to break the reactant bonds
endothermic - more energy put in during breaking of reactant bonds than released during formation of product bonds

Question 9

standard conditions

Answer 9

temp = 298K (25 degrees C), pressure = 1 atm

all solids and liquids are assumed to be pure and solutions are considered to be at a concentration of 1 M

Question 10

standard heat of formation

Answer 10

amount of energy required to make one mole of a compound from its constituent elements in their natural or standard state

Question 11

Hess’s Law

Answer 11

if a reaction occurs in several steps, then the sum of the energies absorbed or given off in all the steps will be the same as that for the overall reaction

Question 12

formula for delta Hrxn

Answer 12

(sum of the bond dissociation energy of bonds broken) - (sum of bond dissociation energy of bonds formed)

Question 13

second law of thermodynamics

Answer 13

all processes tend to run in a direction that leads to maximum disorder

Question 14

entropy

Answer 14

used to measure disorder or randomness

delta S is negative is randomness decreases, positive if
randomness increases

Question 15

phase entropies

Answer 15

gas>liquid>solid

Question 16

third law of thermodynamics

Answer 16

absolute zero is defined to be a state of zero entropy

Kelvin = 0, S=0

Question 17

Gibb’s Free Energy

Answer 17

energy that is free to do useful work from a chemical reaction

delta G = delta H - T(delta S)

T = absolute temp in kelvins

Question 18

Gibbs free energy rules

Answer 18

delta G < 0, spontaneous in forward direction
delta G = 0, reaction is at equilibrium,
delta G >0 nonsnpontaneous in forward direction

Question 19

thermodynamics vs kinetics

Answer 19

thermodynamics predicts spontaneity and equilibrium of reaction

kinetics predicts rate of reaction