1

Question 1

give 2 features of reaction in dynamic equilibrium

Answer 1

-concentration of products and reactants remains constant
-rate of forwards and backward reaction proceeds at equal rates

Question 2

what must remember in kinetic question for working out moles

Answer 2

mass = Mr/avogadro number
this gives answer in g
must convert to kg
by dividing again by 1000 result

Question 3

Mn and hydrogen peroxide equation

Answer 3

MnO4- -> Mn2+
H2O2 -> O2

Balance and combine to get

2MnO4- + 6H+ + 5H2O2 -> 2Mn2+ + 8H2O + 5O2

Question 4

Li+ half cell equation

Answer 4

Li(s)|Li+(aq) || H+(aq)|½H2(g)|Pt(s)

Question 5

Li redox equations

Answer 5

Positive electrode: Li+ + CoO2 + e– → Li+ [CoO2 ]–

Negative electrode: Li → Li+ + e–

Question 6

state the meaning of transition metal complex

Answer 6

central metal ion surrounded by ligands

Question 7

salt that can be used in salt bridge

Answer 7

KNO3

Question 8

phosphorus and oxygen reaction

Answer 8

P4 + 5O2 -> P4O10

Question 9

if surface area of platinum electrode increases, whats the effect on EMF of cell

Answer 9

no change

Question 10

Define the term Brønsted–Lowry acid

Answer 10

proton donor

Question 11

State the meaning of the term Brønsted–Lowry base

Answer 11

proton acceptor

Question 12

equation for the reaction of ethylamine (CH3CH2NH2) with water to form a weakly alkaline solution

Answer 12

CH3CH2NH2 + H2O →CH3CH2NH3+ + OH-

Question 13

when finding ph of diproic acid, what to do, given you have concentration of strong acid…

Answer 13

x2 the concentration then find ph

Question 14

when can you simplify so that [H+] = [salt-] equals to [H+]^2

Answer 14

when ratio of salt and acid
( H+ and salt-)
is 1:1

Question 15

What are the standard conditions which apply to Fe3+(aq)/Fe2+(aq) in electrode potential?

Answer 15

*298 K temperature
*Both Fe3+ (aq) and Fe2+ (aq) have concentration of 1 mol dm–3
*pressure is at 100 kPa

Question 16

Identify the weakest oxidising agent and EXPLAIN why is it the weakest oxidising agent?

Answer 16

Fe2+ as it has the most negative electrode potential (E°)

Question 17

Identify all the species in the table which can be oxidised in acidic solution by BrO(aq)

Answer 17

Fe2+

Cl–

Question 18

Write the conventional representation for this cell.

Answer 18

Pt|H2(g)|H+(aq)‖ Fe3+(aq),Fe2+(aq)|Pt

Question 19

Give the conventional representation of the cell that is used to measure the standard electrode potential of iron as shown in the table.

Answer 19

Pt|H2(g)|H+(aq)‖ Fe2+(aq)|Fe(s)

Question 20

why do amino acids separate on the TLC plate

Answer 20

Difference in the balance between retention on the stationary phase and solubility in the mobile phase

Question 21

why developing agent needed in TLC

Answer 21

amino acids are colourless
so they need to be made visible

Question 22

state steps to locate positions of the amino acids on the TLC plates to determine their Rf values

Answer 22

spray with ninhydrine (or use UV light)
measure distance from initial pencil line to middle of spots (x)
measure distance from initial pencil line to solvent front line (y)

Question 23

wearing plastic gloves in TLC

Answer 23

prevent contamination from hands to the plate

Question 24

adding developing agent of depth no more than 1 cm3 in TLC

Answer 24

if solvent is too deep
it will dissolve the mixture from the plate

Question 25

allow plate to dry in TLC

Answer 25

solvent can be toxic (or flammable)

Question 26

how to determine accurate MP

Answer 26

-use small sample in capillary tube -heat slowly, especialy when approaching expected MP -record the values from when the sample first starts to melt to when it fully metls into a liquid

Question 27

observation when all iodine has reacted

Answer 27

from brown solution to colourless solution

Question 28

describe and explain shape of graph

Answer 28

* exponential increase * as concentration increases so does the rate * many more particles have energy greater than activation energy

Question 29

2 amino acids always form what bond

Answer 29

amide

Question 30

which is stronger disulfide bonds or hydrogen bonds?

Answer 30

Disulfide bonds are covalent bonds formed between two cysteine amino acids, while hydrogen bonds are weaker, intermolecular forces

Question 31

suggest change in studen'ts method to reduce percentage uncertainty in temperature change

Answer 31

* use larger mass of solid * so temperature change is greater

Question 32

suggest difference between experimental and theorotical value of enhtalpy change

Answer 32

incomplete combustion or incomplete reaction

Question 33

a reaction is catalysed by Manganese (IV) oxide explain why the reaction was fastest at the start

Answer 33

* highest concentration of reactants * so more frequent successful collisions

Question 34

oxidation states of F2O

Answer 34

F is -1 O is +2 because F is always negative

Question 35

autocatalysis is an example of which catalysis?

Answer 35

autocatalysis is an example of homogeneous catalysis

Question 36

example of autocatalysis

Answer 36

* oxidation of ethanedioic acid (C2O4 2-) by manganate(VII) ions (MnO4-) * uncatalysed reaction has high activation energy as the 2 negative ions repell each other

Question 37

uncatalysed reaction of C2O42- and MnO4-

Answer 37

Question 38

first and second step of autocatalysis of Mn2+

Answer 38

* first stage: MnO4- to Mn2+ **and** Mn2+ to Mn3+ * second stage: C2O42- to CO2 **and** Mn3+ to Mn2+

Question 39

how to track autocatalysis reaction

Answer 39

* MnO4- ions are deep purple colour * can use colorimeter * reaction will go from purple to colourless

Question 40

describe graph

Answer 40

* slows at the start as there is no catalyst and two negative ions repel each other hence high Ea * as some Mn2+ is formed the rate increases as reactions is being increasingly catalysed * Rate decreases and levels off as reactants get used up