paper 1 chem

explain chelate effect

1) multidentate ligands replace monodentate ligands

2) because there is an increase in entropy

graph for how S2O82- ions change over time

explain how fe2+ catalyse the reaction

2a (reaction slow) because S2O82– and I– repel/high

Ea

Or

(reaction slow) because two negative ions repel/high

Ea

2b Fe2+ attracts the S2O82– so lower Ea

Or

Fe2+ and S2O82– oppositely charged so lower Ea

2c Iron/Fe has a variable oxidation state

colour of iron carbonate

GREEN

role of sulfuric acid with nacl

PROTON ACCEPTOR

why does the second electron affinity of oxygen have a positive value

(O-) negative ion repels electron

explain why the enthalpy of lattice dissociation for sodium oxide is greater than the enthalpy of lattice dissociation for sodium chloride

oxide ions have a higher negative charge stronger attraction between the oppositely charged ions

why is there not a data book value for the enthalpy of solution of sodium oxide

sodium oxide reacts with water to produce NaOH

why do you use a stoppered flask after filtration

• to prevent reaction with CO2

• to prevent evaporation of water from the solution

state the meaning of a transition metal complex

(Central) metal atom/ion surrounded by ligand

suggest why … is neutral

ligand neutral + complex is neutral

example of e/z isomerism

effect on emf if water added to rhs electrode

emf increases

displayed formula for SO42-

describe how solution is made up to 250 cm³

M1 Transfers the solution to a volumetric/graduated flask

M2 Add washings using distilled water and make up to the graduation mark/250 cm3

M3 Invert many times / shake to mix

why is it good practice to rinse pippete with some alkali

So that the titration is done with known concentration of alkali

Allow so that water does not dilute the solution

aluminium sulfate and water

Al2(SO4)3 + 12 H2O → 2 [Al(H2O)6] 3+ + 3 SO4 2–

aluminum hexa aqua copper and excess ammonia

methanol and water half equation

CH3OH + H2O —> O2 + 6H+ + 6 e-

why does a fuel cell not need to be electrically charged

Reactants supplied continuously

advantage of using methanol over hydrogen

Methanol (is liquid so) can be stored easily or transported easily

how is relative abundance determined TOF

CURRENT is proportional to abundance

explain why titration cannot be done using an indicator

weak acid weak base titration

ph change is too gradual (no vertical section of graph)

perfect ionic model smaller than calculated value

• some covalent character

• the bonds holding the lattice together are stronger

describe a test between sodium oxide and phosphorus oxide

1) add water

2) add blue litmus paper

3) blue with sodium oxide and red with phosphorus oxide

copper hexa aqua 2+ and excess ammonia equation

why can calorimetry not be used to determien conc of solutions containing (cucl2)-

1) has a full 3d subshell

2) cannot absorb frequencies of visible light/ it is colourless

why is enthalpy change for chelate effect close to 0

SAME number and TYPE of bond being broken and made