thermochemistry

Question 1

1.exothermic reactions

2.endothermic reactions

Answer 1

1. heat released, system cools down (-ve)
   >most spontaneous reactions
   {combustion}
   arrow down

2.heat absorbed, temp high (+ve)
>non spontaneous are endo
arrow up

Question 2

combustion of carbon enthalphy change value

Answer 2

-393.7 KJ/mol

Question 3

haber process is an_____ process

Answer 3

exothermic

Question 4

process which is;
1. always exo
2. always endo

Answer 4

1. COMBUSTION
2. IONISATION ENERGY

Question 5

spontaneous and non spontaneous reactions

Answer 5

takes place without any outside assistance (e.g burning)
>its single directional
>irreversible
>mostly exothermic
[rusting of iron, burning of coal and hydrocarbon]

takes place with assistance
>reversible
>endothermic
[pumping water uhill, dissufion of gass from high to low]
*formation of nitric oxide N2 and O2 in air.

Question 6

is heat and work a state function

Answer 6

NO.

state function is a thermodynamic state if macroscopic properties of P, V, T, n are known

Question 7

is heat(q) a state property

Answer 7

NO.
heat: qty of energy that flows across the boundaryof a system due to a difference in temperature bw system and surrounding
>not a property

Question 8

work

Answer 8

W=Fs.
workdone by the system= +ve
workdone on the system= -ve

Question 9

1st law of thermodynamics equation

Answer 9

change in energy(E)=q+w

Question 10

Enthalpy(H)

Answer 10

Sum of internal energy and product of pressure and volume.

         H=E+PV

1.state fuction
2.measured in joules

Question 11

St Enthalpy of reaction 🔺Hr

Answer 11

Amount of heat evolved/abdorbed at standard conditions states

Question 12

Standard confitions

Answer 12

298K, 25⁰C

Question 13

Enthalpy of formation

Answer 13

1 mol of a compound formed from its elements under standard states and conditions

May be exo or endo.

Question 14

Enthalpy of atomisation

Answer 14

ENDO

1 mol of gaseous atoms formed from element under standard conditions

Question 15

Enthalpy neutralisation

Answer 15

1 mol of H+ from an acid react with 1 mol OH- from a a base form one mol of water under st condition

Question 16

Enthalpy combustion

Answer 16

EXO

1 mol substance completely burnt in Oxygen.

Question 17

Enthalpy solution

Answer 17

EXO OR ENDO

1 mol of substance dissolved in solvent until no heat change

Question 18

measurement of enthalpy of a reaction

Answer 18

glass calorimeter [reaction]
bomb calorimeter [combustion]

{measured at const volume}

Question 19

heat capacity

Answer 19

q=c(sp heat)T

Question 20

Born haber cycle

Answer 20

Energy change always 0
Used to calculate lattice energy of ionic compounds.

Question 21

Lattice energy definition and dependant on?

Answer 21

Enthalpy of formation of 1mol of ionic compound from its gaseous ions.

Can be endo or exo

(Na+) + (Cl-)……..>NaCl. 🔺Hlatt= -787kjmol

Depends directly on +ve charge
E.g mg2+ has higher than Na+

Depends inversely on size
Lower size is higher lattice energy

Question 22

NaCl enthalpy of formation value

Answer 22

-411