Module 5

Question 1

Conc. time graphs?

Answer 1

Zero - \
1st - curve down
2nd - large surge down

Question 2

Rate conc. graph?

Answer 2

Zero =  — 
1st = / 
2nd = curve up

Question 3

Rate determining step

Answer 3

The slowest step within the sequence

Question 4

Arrenhius equation?

Answer 4

K = A e-Ea/RT

Log
LnK = -Ea/RT + LnA
Y = mx + c

Gradient = -Ea/R
Y axis intercept = lnA

Question 5

Mole fraction?

Answer 5

No of moles of A / no of moles in gas mixture

Question 6

Partial pressure?

Answer 6

Mole fraction of A X total pressure

Question 7

Weak acid calc?

Answer 7

Ka

HA <=> H+ + A-

Question 8

Strong bad/ strong acid?

Answer 8

Kw
Kw = [H+][OH-]
1 x 10-14

Weak base = POH = -log(OH-)
pH = 14 - POH

Question 9

Buffer

Answer 9

System that minimises pH changes when small amounts of an acid or base are added

Weak acid and conjugate base

Question 10

Titration curves?

Answer 10

Neutralisation

Equivalence point - volume of one solution that exactly reacts with the volume of the other

End point - indicator contains equal concentrations of HA and A-, colour between the two

Question 11

Lattice enthalpy?

Answer 11

The enthalpy change that accompanied the formation of one moles of an ionic compound from its gaseous ions

K+ + cl- —> kcl (s)

Exothermic always negative

Question 12

Enthalpy change of formation

Answer 12

EC that takes place when one mole of a compound is formed from its elements

Na (g) + 1/2Cl2 (g) —> Nacl (s)

Question 13

Enthalpy change of atomisation?

Answer 13

EC that takes place for the formation of one mole of a gaseous atom from the element

Question 14

First ionisation energy

Answer 14

The enthalpy change required to remove one electron from each atom of one mole of gaseous atoms to form one mole of gaseous +1 ions

Question 15

First electron affinity

Answer 15

Energy change that takes place when one electron is added to an atom in one mole of gaseous atoms to form one mole of gaseous -1 ions

Question 16

Enthalpy change of solution

Answer 16

Enthalpy change that take solace when one mole of a solute dissolves in a solvent

Question 17

Enthalpy change of hydration

Answer 17

Enthalpy change that accompanies the dissolving of gaseous ions in water to form aqueous ions

Question 18

Factors affecting lattice enthalpy

Answer 18

Ionice size - increase, attraction between ions decreases, lattice enthalpy less negative, MP decrease

Ionic charge - increases, attraction increase, lattice enthalpy more negative

Question 19

Factors affecting hydration enthalpy

Answer 19

Ionic size - increase, attraction between water molecules and ions decreases, hydration energy less negative

Ionic charge - increase, attraction with water molecules increase, more negative

Question 20

Entropy?

Answer 20

🔼s
The greater the entropy the greater the dispersal of energy hence the greater the disorder

At 0K no energy entropy 0
Always Positive entropy

Question 21

Standard entropy?

Answer 21

Entropy of one mole of a substance, standard conditions

Question 22

Gibbs free energy

Answer 22

🔼G = 🔼H - t🔼S

🔼G < 0 to be feasible

Question 23

Primary fuel cell

Answer 23

Non rechargeable
Electrical energy produced by oxidation and reduction of electrodes
Reactions cannot be reversed, chemicals used up and voltage will fall.
Generally alkaline based

Question 24

Secondary fuel cell?

Answer 24

Rechargeable

Reversed during recharging, chemicals regenerated

Question 25

Fuel cells?

Answer 25

Use energy from the reaction of a fuel with oxygen to create a voltage

Question 26

Transition elements

Answer 26

Dblock elements that form at least one ion egg a partially filled d-orbital Form compounds with different oxidation states Form coloured compounds Can act as catalysts

Question 27

Complex ions

Answer 27

Formed when one or more negatively charged ions bond to central metal ions (Ligands) Ligand - molecule or ion that donates pair of e- to central metal ion to form coordinate bond

Question 28

Ligand substitution | Copper and ammonia

Answer 28

Cooper ions and ammonia [Cu(H2O)6]2+ pale blue add ammonia First see pale blue ppt Cu(OH)2 Then ppt dissolves in excess ammonia create dark blue solution [Cu(NH2)4(H2O)2]2+

Question 29

Ligand substitution | Copper and chloride

Answer 29

[Cu(H2O)6]2+ pale blue Add 4Cl- [CuCl4]2- yellow solution

Question 30

Ligand substitution | Chromium ions

Answer 30

Chromium sulphate dissolved in water | [Cr(H2O)5SO4]+ green solution

Question 31

Precipitation reaction?

Answer 31

Two aqueous solutions containing ions react together to form an insoluble ionic solid precipitate.

Question 32

Qualitative analysis

Answer 32

``` Cu2+ blue —> blue ppt Fe2+ pale green —> green ppt Fe3+ pale yellow —> orange/brown ppt Mn2+ pale pink —> pink/brown ppt Cr3+ violet —> grey/green ppt ``` Addition of OH-