M5 Knowledge gaps

Question 1

Finding k from t1/2 (half-life)

Answer 1

k = (ln 2) / t1/2
Where reaction is first order

Question 2

A(g) + 2B(g) –> C(g) + D(g) ΔH = -37kJmol-1
Effect of increasing temp. on Kc and rate of reaction

Answer 2

Kc decreases as product:reactant ratio has decreased (shift to LHS)
Rate increases

Question 3

A(g) + 2B(g) –> C(g) + D(g) ΔH = -37kJmol-1
Effect of increasing pressure on Kp and rate of reaction

Answer 3

Kp constant at constant temperature (initial shift to RHS, ratio increases, shift back to LHS to restore Kp)
Increases rate

Question 4

A(g) + 2B(g) –> C(g) + D(g) ΔH = -37kJmol-1
Effect of increasing [A] on Kc and rate of reaction

Answer 4

Kp constant at constant temperature (intiial shift to RHS, ratio increases, shift back to LHS to restore Kc)
Increased rate if volume constant

Question 5

Ka / pH calculation approximations

Answer 5

undissociated [HA] = equilibrium [HA]
equ. [H+] = equ. [A-] (negligible H2O dissociation)

Question 6

Buffer solution

Answer 6

Minimises pH changes on addition of small amounts of acid or base

Question 7

Lattice enthalpy

Answer 7

Formation of 1mol of ionic lattice from gaseous ions

Question 8

Entropy

Answer 8

Measure of the dispersal of energy in a system
More disordered = greater entropy

Question 9

Calculating ∆S

Answer 9

∆S = ∆S of products - ∆S of reactants

Question 10

What does +ve ∆G indicate?

Answer 10

Reaction is not feasible at given temperature

Question 11

Calculating ∆G

Answer 11

∆G = ∆H - T∆S

Question 12

Factors affecting feasibility of reaction

Answer 12

Temperature
Enthalpy change
Entropy change

Question 13

Oxidising agent

Answer 13

Species that accepts electrons

Question 14

Reducing agent

Answer 14

Species that donates electrons

Question 15

Colour change for Fe2+ / MnO4- redox titration

Answer 15

Pink-purple to colourless

Question 16

Finding end point of I2 / S2O3 2- redox titration

Answer 16

Add starch
Blue-black to colourless

Question 17

Transition element

Answer 17

d-block element that have an ion with an incomplete d sub-shell
variable oxidation states
Not Sc or Zn

Question 18

Examples of catalytic transition elements

Answer 18

Iron catalyst used in Haber process
V2O5 used in Contact Process

Question 19

Ligand

Answer 19

Donates a pair of electrons to central metal ion forming coordinate / dative covalent bond

Question 20

Type of stereoisomerism in Pt(NH3)2Cl2

Answer 20

cis-trans

Question 21

Uses of cis-platin

Answer 21

Anti-cancer drug
Binds to DNA preventing cell division

Question 22

Fe2+ and Fe3+ colours

Answer 22

Fe2+ is green
Fe3+ is brown

Question 23

Cr2O7 2- Cr3+ and Cr2+ colours

Answer 23

Cr2O7 2- is orange
Cr3+ is green
Cr2+ is blue