Enthalpy, Entropy And Free Energy

Question 1

What is the mean bond enthalpy

Answer 1

Average enthalpy change when one mole of a given bond is broken in a range of molecules

Question 2

What is the standard enthalpy of formation

Answer 2

Enthalpy change when one mole of a substance is formed from its elements (in their standard states) under standard conditions

Question 3

What is the standard enthalpy change of combustion

Answer 3

Enthalpy change when one mole of a substance is completely burnt in oxygen

Question 4

What is the standard enthalpy of atomization

Answer 4

Enthalpy change when one mole of a gaseous atoms form from the elements in standard state

Question 5

What is first ionization energy

Answer 5

Enthalpy change when one mole of atoms in gaseous state is converted to one mole of gaseous ions with a positive charge

Question 6

What is second ionization energy

Answer 6

Enthalpy change when one mole of atoms in gaseous 1+ state is converted to one mole of gaseous 2+

Question 7

What is the first electron affinity

Answer 7

Enthalpy change when one mole of gaseous atoms forms one mole of gaseous ions with a negative charge

Question 8

What is second electron affinity

Answer 8

Enthalpy change when one mole of gaseous 1- atoms forms one mole of gaseous ions with a -2 negative charge

Question 9

What is lattice enthalpy of formation

Answer 9

Enthalpy change when one mole of a solid ionic compound is formed from gaseous ions

Question 10

What is the lattice enthalpy dissociation

Answer 10

Enthalpy change when 1 mole of a solid ionic compound is dissociated into gaseous ions

Question 11

What is the standard enthalpy of hydration

Answer 11

Enthalpy change when one mole of gaseous ions from aqueous ions

Question 12

What is the standard enthalpy of solution

Answer 12

Enthalpy change when 1 mole of solute forms a solution

Question 13

Describe the enthalpy changes and diagram for born harbor cycle

Answer 13

Reactants in standard states-
Atomization
reactants (metals) in gaseous state
First ionization energy
Metal in + state
Atomization
Non metal in single form (X2->X)
Electron affinity
Non metal in - state
Lattice enthalpy of formation
Solid compound

Question 14

For a reaction to be feasible what value does delta G have to have

Answer 14

Negative

Question 15

What state has the highest entropy value

Answer 15

Gas, liquid, solid

Question 16

What is the equation for delta G

Answer 16

Delta G= delta H -T delta S

Question 17

how to calculate delta S (entropy)

Answer 17

Products - reactants

(sums of entropy)

Question 18

how to calculate delta H (formation)

Question 19

what causes a higher lattice enthalpy

Answer 19

increasing charge

smaller the ion size

large exothermic values of lattice enthalpy= large electrostatic force of attraction

Question 20

why do smaller ions have larger lattice enthalpies

Answer 20

greater attraction due to higher charge density, larger lattice enthalpies and melting points due to extra energy needed to separate the ions

Question 21

what increases the enthalpy of hydration

Answer 21

smaller ions

larger the charge of the ion

Question 22

for diagram with enthalpy of solution and hydration at what levels do atoms go on

Answer 22

solid compound –> (enthalpy of solution)
(Aq) ions <– (hydration)
one (aq) ion and one in standard state <–(hydration)
gaseous ions–> (lattice enthalpy) to solid

Question 23

what value of delta solH means its more likely to dissolve

Answer 23

the more negative

Question 24

will a substance dissolve if delta solH is positive and very large

Answer 24

no

Question 25

if delta solH is small and positive will it dissolve

Answer 25

may dissolve if there is sufficient energy

Question 26

How does the Y=MC + C equation link to delta G equation

Answer 26

Y=MX+C Delta G= -delta S T + delta H

Question 27

How to calculate Q=MCdelta T equation with delta H, calculate delta T

Answer 27

Work out moles and X by delta H to get energy (J) T= J/MC