Definitions thermodynamics

Question 1

Heat of reaction/reaction enthalapy

Answer 1

the enthalapy change accompanying the a chemical reaction at a certain temp and pressure

Question 2

Std Reaction Enthalapy

Answer 2

the enthalapy change accompanying the conversion of 1 mol of reactant into product at stp(1 bar, 298K)

Question 3

Enthalapy of formation. When is it std?

Answer 3

the enthalapy change accompanying the formation of 1 mol of a compound from it’s respective elements at their most stable state of aggregation at a certain temperature and pressure is called enthalapy of formation.

At 298K and 1 Bar, it is called std enthalaapy of formation

Question 4

Enthalapy of combustion. When is it std?

Answer 4

It is defined as the enthalapy change accompanying the complete combustion of 1 mol of a compound in the presence of oxygen at a particular temperature and pressure.

It becomes std if p=1 bar and temp= 298K

Question 5

Enthalapy of neutralisation. When is it std?

Answer 5

It is defined as the enthalapy change accompanying the complete neutralisation of 1 mol H+ ions from acid and OH- ions from base to form 1 mol of water at a particular temp and pressure is called the enthalapy of neutralisation.

it is std when p=1 bar and t= 298k

Question 6

Enthalapy of dilution. When is it std? Infinite dilution?

Answer 6

The enthalapy change accompanying the addition of a given amount of solute to a given amount of solvent at a certain temp and pressure.

it is std when p=1 bar and t= 298K

Infinite dilution is amount of solvent»amount of solute

Question 7

Enthalapy of fusion. When is it std?

Answer 7

The enthalapy change accompanying the conversion of 1 mol of solid into liquid at it’s melting point and certain pressure, is called enthalapy of fusion.

when p=1 bar, it is std enthalapy

Question 8

Enthalapy of vaporization. When is it std?

Answer 8

The enthalapy change accompanying the conversion of 1 mol of liquid into gas at its boiling point and certain pressure.

p=1 bar

Question 9

Enthalapy of sublimation. When is it std?

Answer 9

the enthalapy chnage accomapnying the coversion of 1 mol of solid into gas at sublimation point and certain pressure.

p=1 bar

Question 10

Enthalapy of transformation

Answer 10

the enthalapy change accompanying the complete transformation of 1 mol of an allotrope of an element into another at transformation point and constant pressure.

p=1 bar

Question 11

Hydration enthalapy

Answer 11

The anthalapy change in completely hydrating 1 mol of an anhydrous or a partially hydrated compound at particular temperature and pressure.

Question 12

Lattice enthalapy

Answer 12

the enthalapy change accompanying formation of 1mol of an ionic compound from it’s constituent gaseous ions at a particular temp and pressure

Question 13

Hess Law of Constant Heat Summation

Answer 13

If a reaction takes place in several steps then it’s standard reaction enthalapy is the sum of the the std enthalapies of the intermediate reactions into which the overall reactions can be divided at the same temperature.

Question 14

Enthalapy of atomisation

Answer 14

enthalapy change accompanying the breaking of 1 mol of a particular type of bond to produce gaseous constituent atoms at a particular temp and pressure.

Question 15

Spontaneity

Answer 15

A process that can take place on it’s own under given conditions once it has been initiated (if required).

Question 16

Non-spontaneous/non-feasible

Answer 16

a process that requires continuous supply of external energy (or external aid) to be carried out

Question 17

Example of endothermic rxns that are spontaneous?

Answer 17

i) Melting of ice
ii) HgO(g) —heat—> Hg(l) + 1/2O2(g)
iii) 1/2N2 + O2 –> NO2(g)

Question 18

2nd Law of thermodynamics

Answer 18

for an isolated system, increase in entropy is the natural direction of a spontaneous process.
OR
the enthalapy of the universe is constantly increasing as it is as most of the processes are irreversible.