thermodynamics

Question 1

energy cannot be created or destroyed during a chemical reaction

what happens to the energy in a reaction where high energy reactants form low energy products?

Answer 1

given out to the surroundings

Question 2

endothermic or exothermic?
energy is given out to the surroundings during a chemical reaction

Answer 2

exothermic

Question 3

what does all matter have?

Answer 3

mass
temperature
volume
entropy

Question 4

what is entropy?

Answer 4

a measurement of disorder

Question 5

who was entropy introduced by?

Answer 5

rudolf clausius
1865

Question 6

what is the symbol of entropy?

Answer 6

S

Question 7

what affect does higher temperature have on entropy?

Answer 7

higher entropy
more disorder
particles gain more kinetic energy

Question 8

what happened to its entropy when a solid dissolves in water?

Answer 8

it’s entropy increases

Question 9

what happens to the entropy when a single reactant breaks down into two or more products?

Answer 9

entropy always increases

Question 10

entropy increasing and decreasing in terms of positivity and negativity

Answer 10

increased entropy- positive entropy change

decreased entropy- negative entropy change

Question 11

what is the entropy change for the following reaction:

S8 —> 4S2

Answer 11

entropy change is positive

Question 12

what is the entropy change if a reaction has more moles of product than reactants likely to be?

Answer 12

positive

Question 13

what happens to entropy when there’s more possible configurations of the arrangement of kinetic energies ?

Answer 13

entropy increases

Question 14

equation of entropy

Answer 14

S = k log (W)

S= entropy
W= number of configurations
k= a constant
log= the logarithm of

as W increases, S increases too

Question 15

how is the simple system similar to a real life atomic system?

Answer 15

they both contain particles in boxes
their particles are both restricted to certain kinetic energies
you can’t measure the kinetic energy of each particle in either system

Question 16

when we crunch the numbers, we find that changing state from
solid- liquid
or
liquid- gas
increases entropy
why is that?

Answer 16

there are more available kinetic energy levels for gases than liquids
there are more available kinetic energy levels for liquids than solids

Question 17

entropy change equation
**

Answer 17

entropy change = q/T
units= J/K

q-heat
T-temperature

Question 18

what is the entropy of all substances at 0 K?

Answer 18

0 J/K

Question 19

why is the entropy of a substance 0 at 0K?

Answer 19

the particles are not moving

the particles have no disorder

Question 20

for any substance, a graph can be made of how it’s entropy changes with temperature. what do these graphs show?

Answer 20

start at the origin
show that entropy increases with temperature
have a large jump at the melting point of the substance
have a large jump at the boiling point of the substance

Question 21

standard molar enthalpy definition

Answer 21

the entropy of 1 mole of a substance at 298K

Question 22

units for the entropy change of a reaction

Answer 22

J/K/mol

Question 23

for any chemical reactions what are the surroundings defined as?

Answer 23

anything which isn’t in the reaction equation

Question 24

what do exothermic reactions do to their surroundings?

Answer 24

increase the entropy of their surroundings

Question 25

what do endothermic reaction do to their surroundings?

Answer 25

decrease entropy of their surroundings

Question 26

what effect will a negative entropy change of a reaction have on the surroundings?

Answer 26

the entropy of the surroundings will increase
the entropy of the surroundings will be positive

Question 27

entropy change of surroundings
equation

Answer 27

-entropy change of reactions/ temperature

Question 28

units for entropy change of surroundings

Answer 28

kJ/K/mol

Question 29

what do you do to convert from
kJ/K/mol to J/K/mol

Answer 29

x1000

Question 30

what do you work out if we add the entropy change of a reaction system and the entropy change of the surroundings?

Answer 30

the entropy change of the universe

Question 31

what is the reason a chemical reaction can happen because of?

Answer 31

it increases the entropy of the universe

Question 32

what do we say instead of saying the entropy change of the universe will or won’t happen?

Answer 32

we say it is feasible or not feasibke

Question 33

what must happen for a reaction happen?

Answer 33

occur at reasonable rate
increase the entropy of the universe

Question 34

why do some reactions not happen when scientists mix the reactants in a lab?

Answer 34

the activation energy for the reaction is too high
the rate of reaction is too slow

Question 35

1 st law of thermodynamics

Answer 35

energy cannot be created nor destroyed

Question 36

2nd law of thermodynamics

Answer 36

for any process to happen, it must increase the entropy of the universe

Question 37

for a reaction to be feasible what must gibbs free energy change be ?

Answer 37

negative

Question 38

gibbs free energy change
equation

Answer 38

gibbs free energy change =
-T (entropy change of the universe)

Question 39

change in gibbs free energy busing different types of entropy
equation

Answer 39

delta G= change in enthalpy of a reaction- change in Temperature x entropy change