question

Oxidation: Fe2+ forms

answer

Fe3+ + e-

question

Reduction: MnO4- + 8H+ +5e- forms

answer

Mn2+ + 4H2O

question

Redox: MnO4- + 8H+ +5Fe2+ forms

answer

Mn2+ + 5Fe3+ + 4H2O

question

Redox titrations using MnO4-

answer

Solution ACIDIFIED with sulphuric acid, not hydrochloric acid which REACTS with MnO4- and produces CHLORINE GAS. MnO4- is in BURETTE and iron is in the CONICAL flask. Stop when there is a PERMANENT PINK colour.

question

Redox titration

answer

Transfer of electrons not protons as in normal titrations. Titrate an oxidising agent against a reducing agent.

question

Why use MnO4- (potassium manganate)?

answer

Self-indicating; Mn2+ ions pale pink, MnO4- ions deep purple. When in excess, MnO4- ions form deep purple solution.

question

Oxidation change from MnO4- to Mn2+

answer

-5

question

Oxidation change from Fe2+ to Fe3+

answer

+1

question

Ratio of Fe2+ to MnO4-

answer

5:1

question

Large Kstab value

answer

Equilibrium lies to the RIGHT. Indicates complex ion is MORE STABLE. Ion is formed MORE EASILY.

question

Small Kstab value

answer

Equilibrium lies to LEFT. Indicates complex ion is LESS STABLE. Ion is MORE DIFFICULT to form.

question

Tables of Kstab values

answer

Compare stability of complexes with those containing H2O ligands

question

Why is water left out of Kstab equation

answer

All species are dissolved in water which is in large excess and concentration is constant

question

Why is carbon monoxide fatal

answer

Binds to haemoglobin more strongly than oxygen at the same binding site; irreversible ligand substitution. Tissues do not receive oxygen so cannot respire.

question

What is carbon monoxide

answer

Formed in incomplete combustion of carbon compounds/ tobacco. Colourless/ odourless.

question

Haemoglobin

answer

Protein complex composed of 4 polypeptide chains and 4 haem groups in red blood cells.

question

Haem group

answer

Complex ion with Fe2+ ion at centre; 4 coordinate bonds to nitrogen atoms of the haem structure; coordinate bond to protein globin; coordinate bond for oxygen.

question

Why there are more water ligands than chloride ligands in a complex

answer

Chloride ligands are larger than water ligands and have larger forces of repulsions so fewer can fit around a metal ion

question

Stages of ammonia addition to [Cu(H2O)6]2+ solution

answer

Stage one; small amount of ammonia added; formation of Cu(OH)2; pale blue precipitate. Stage two; excess ammonia added; formation of [Cu(NH3)4(H2O)2]2+; dark blue precipitate

question

Requirements for optical isomers of complex ions

answer

OCTAHEDRAL. Three bidentate ligands. Two bidentate ligands and two monodentate ligands. One hexadentate ligand.

question

EDTA

answer

(Ethylenediaminetetraacetic acid) Hexadentate ligand with a 4- charge

question

Uses of EDTA

answer

Chelating agent; binds to metal ions so dereases their concentration in a solution. DETERGENT; binds to calcium and magnesium to reduce hardness of water. STABILISER; removes metal ions catalysing oxidation in some foods. MEDICAL; prevents clotting and relieves lead and mercury poisoning.

question

Cis isomerism in complex ions

answer

Monodentate ligands are adjacent; 90 degrees apart

question

Trans isomerism in complex ions

answer

Monodentate ligands are opposite; 180 degrees apart

question

Examples of bidentate ligands

answer

ethane-1,2-diamine and ethanedioate

question

Criteria for cis-trans isomerism in complex ions

answer

Two types of ligand. 4 of one monodentate and 2 of another monodentate. 2 bidentate and 2 monodentate. 2 of one monodentate and two of another.

question

Shape of complex ions with 4 monodentate ligands of 2 types

answer

Square planar

question

Bond angles in an octahedral

answer

90 degrees

question

Haber process

answer

Forms ammonia from nitrogen and hydrogen for fertilisers

question

Haber process equation

answer

N2+3H2 forms 2NH3

question

Contact process

answer

COnverts sulphur dioxide to sulphur trioxide in the manufacture of sulphuric acid.

question

Contact process equation

answer

2SO2+O2 forms 2SO3

question

Hydrogenation of alkenes

answer

Forms saturated compounds from unsaturated compounds

question

Decomposition of hydrogen peroxide

answer

Forms water and oxygen

question

Decomposition of hydrogen peroxide equation

answer

2H2O2 forms 2H2O+O2

question

Ways transition metals are catalysts

answer

Provide a surface for adsorption and desorption. Can change oxidation states by gaining or losing electrons; bind to reagents to form intermediates in chemical pathway with lower activation energy.

question

Physical properties of transition metals

answer

Shiny, high density, high melting point, high boiling point, can conduct electricity as form giant metallic lattices with delocalised electrons when solid.

question

Alloy of nickel and copper

answer

Makes silver coins

question

Titanium is a component of

answer

Joint replacement parts

question

Iron is used in

answer

Telephone and post boxes, construction of buildings and bridges

question

Why do transition metals form coloured ions

answer

Partially filled D orbitals

question

Oxidation state formed by every transition metal

answer

+2; electrons lost from the 4s orbital

question

Highest oxidation state of a transition metal is often found in

answer

Strong oxidising agents

question

Why scandium is not a transition metal

answer

Forms a 3+ ion in which d orbitals are empty

question

Why zinc is not a transition metal

answer

Forms a 2+ ion in which d orbitals are full

question

Transition elements that do not follow the Aufbau principle

answer

Chromium and copper; electron repulsion between outer electrons is minimised; increased stability of atoms

question

Electron configuration of chromium

answer

Each orbital contains one electron

question

Electron configuration of copper

answer

Each 3d orbital is completely full, only one electron in 4s

question

Transition elements lose electrons from orbitals

answer

4s and 3d, 4s first

question

Limitations of hydrogen economy

answer

Must be publicly and politically accepted. Logistical problems in handling and maintenance of hydrogen systems. More energy may be used in making hydrogen, by electrolysis, than is saved by its use.

question

Limitations of hydrogen fuel cells

answer

Large scale storage and transportation of hydrogen is not cost or energy efficient. Storing pressurised liquid is not feasible. Adsorbers and absorbers of hydrogen have a limited lifetime. Fuel cells have a limited life time and cost to replace and dispose of. Fuel cells are produced with toxic chemicals.

question

Storage of hydrogen

answer

Liquid under pressure at a low temperature; logistical problems. Can be adsorbed onto surfaces of solids. Can be absorbed within some solids.

question

Efficiency of fuel cell vehicles

answer

Petrol engines are 20% efficient at converting chemical energy, hydrogen fuel cell vehicles are 40-60% efficient

question

Hydrogen rich fuels

answer

Methanol, natural gas, petrol; mixed with water and converted into hydrogen gas by on board reformer, which operates at 250-300 degrees

question

Pollution of hydrogen fuel cells

answer

Only produce a small amount of carbon dioxide and air pollutants, do not produce carbon monoxide in incomplete combustion.

question

Advantages of methanol fuel cells

answer

Liquid, so is easier to store than hydrogen gas. Methanol can be generated from biomass.

question

Hydrogen oxygen fuel cell

answer

Hydrogen and oxygen flow in while water flows out. Continue to operate as long as oxygen and hydrogen are input.

question

Negative terminal of hydrogen oxygen fuel cell

answer

2H2O+2e- forms H2+2OH-

question

Positive terminal of hydrogen oxygen fuel cell

answer

1/2O2+H2O+2e- forms 2OH-

question

Overall cell reaction of hydrogen oxygen fuel cell

answer

H2+1/2O2 forms H2O

question

In electrochemical cells, electrons flow from

answer

Negative anode to positive cathode

question

Main types of electrochemical cells

answer

Non-rechargeable batteries. Rechargeable batteries. Fuel cells.

question

Non-rechargeable batteries

answer

Provide electrical energy until chemicals have reacted to such an extent that the voltage falls

question

Rechargeable batteries

answer

Recharging reverses the cell reaction so the chemicals in the cells are regenerated and can be reused

question

Fuel cells

answer

Use external supplies of fuels as oxidants which are consumed and must be continuously supplied to continue to provide electrical energy

question

In electrochemical cells, electrons are provided by

answer

The anode; the negative terminal where oxidation occurs

question

In electrochemical cells, electrons are donated to

answer

The cathode; the positive terminal where reduction occurs

question

EMF of the cell

answer

Standard electrode potential of POSITIVE TERMINAL-Standard electrode potential of NEGATIVE TERMINAL

question

Conventional redox equilibria

answer

Show electrons on left

question

Feasible electrochemical reactions take place between

answer

Species on the right of the equilibrium with the more negative EMF and on the left of the equilibrium with the more positive EMF

question

The larger the difference between EMFs

answer

The more likely it is that a reaction will take place

question

If the difference between EMF values is less than 0.4V

answer

A reaction is unlikely to be feasible

question

Why an electrochemical reaction may not take place

answer

Too slow due to a high activation energy. Reactions may take place under conditions that are not standard. Species may not be aqueous.

question

Measuring standard electrode potential

answer

Standard half cell is connected to a standard hydrogen half cell. Standard half cell; metal strip in metal ion solution at 1 moldm-3. Connected by a wire and salt bridge to hydrogen half cell which contains a platinum electrode, acid at 1 moldm-3 and hydrogen gas entering at 298K and 1 atm.

question

Metal ion/ metal ion half cell

answer

Equimolar solution containing ions of the same element in different oxidation states and an inert platinum electrode connected to a wire.

question

Hydrogen half cell

answer

Solution of 1moldm-3 acid, hydrogen gas entering at 298K and 1atm, an inert platinum electrode coated in platinum black which is linked to a wire.

question

Cells from metal/ metal ions

answer

Two solutions of metal ions at 1moldm-3, each containing their metal electrode connected by a wire to a high resistance voltmeter. A salt bridge connects the two solutions

question

Salt bridge

answer

Filter paper soaked in aqueous solutions of ionic compounds that do not react with either half cell solution. Allows transfer of ions between solutions

question

Ionic compounds for salt bridges

answer

KNO3 or NH4NO3

question

Negative enthalpy, positive entropy

answer

Always negative G, feasible reaction

question

Positive enthalpy, negative entropy

answer

Always positive G, never feasible reaction

question

Negative enthalpy, negative entropy

answer

Negative G at low temperatures, feasible at low temperatures

question

Positive enthalpy, positive entropy

answer

Negative G at high temperatures, feasible at high temperatures

question

Most exothermic reactions are

answer

Spontaneous

question

Spontaneous processes happen when

answer

G is negative

question

Spontaneous processes lead to

answer

Lower energy and increased stability

question

Entropy change is positive when

answer

Change makes a system more random

question

Entropy change is negative when

answer

Change makes a system less random

question

Entropy increases when

answer

There is an increase in gas molecules, a solid lattice dissolves or when the temperature increases

question

Energy tends to change from

answer

Being localised to more dilute

question

Factors affecting hydration enthalpy

answer

IONIC SIZE; smaller, makes hydration enthalpy more negative; exerts more forces of attraction on water so releases more energy. IONIC CHARGE; small highly charged ions; makes hydration enthalpy more negative; greater force of attraction on water molecules

question

Factors affecting lattice enthalpy

answer

IONIC SIZE; smaller; pack more closely together; attract each other more strongly; lattice enthalpy becomes more negative. IONIC CHARGE; small highly charged ions; attract eachother strongly; more negative lattice enthalpy

question

Sum of clockwise enthalpies

answer

Sum of clockwise enthalpies

question

Lattice enthalpy

answer

Formation-(Atomisation+ionisation+electron affinity)

question

Enthalpy changes with upward arrows

answer

Endothermic

question

Enthalpy changes with downward arrows

answer

Exothermic

question

Features of lattice enthalpy

answer

EXOTHERMIC; bonds formed. Measure of IONIC BOND STRENGTH. Covalent structures do not have lattice enthalpy. Cannot be measured DIRECTLY; can't make exactly one mole of an ionic lattice

question

Enthalpy of formation

answer

Usually exothermic; bonds formed

question

Enthalpy of atomisation

answer

Usually endothermic; bonds broken

question

Ionisation energy

answer

Endothermic; electron must overcome attraction to nucleus

question

Second electron affinity

answer

Endothermic; electron repulsion by negative 1- ion must be overcome

question

First electron affinity

answer

Exothermic; electron attracted by nucleus

question

Enthalpy of neutralisation for strong acids

answer

Very similar values because they all dissociate to the same extent

question

Titration process

answer

Acid in conical flask, base in burette

question

Titration curve

answer

Add base, pH increases slightly and acid is in great excess. When near the equivalence point the pH increases more rapidly. A vertical section caused by one drop of base is the equivalence point. Further base added causes little change in pH as base is in excess

question

Indicators

answer

Have one colour in their acid form and one colour in conjugate base form. When at end point, equal amounts of both exist forming a mixed colour.

question

Choosing an indicator

answer

End point must be as close as possible to equivalence point

question

Strong acid strong base titration

answer

Start low and end high

question

Strong acid weak base titration

answer

Start low and end low

question

Weak acid strong base titration

answer

Start high and end high

question

Weak acid weak base titration

answer

Start high and end low

question

Carbonic acid

answer

H2CO3, weak acid

question

Hydrogencarbonate

answer

HCO3-, conjugate base

question

Healthy blood pH

answer

7.35-7.45

question

Condition if blood pH falls below 7.35

answer

Acidosis

question

Condition if blood pH rises above 7.45

answer

Alkalosis

question

Addition of acid to blood

answer

Reacts with conjugate base HCO3- and is removed from blood, shifting equilibrium to the left

question

Addition of alkali to buffer in the blood

answer

Reacts with H+ ions to form water, causing H2CO3 equilibrium to shift to the right

question

How carbonic acid is removed

answer

Converted by an enzyme to aqueous carbon dioxide, which is converted to gas in the lungs and exhaled

question

Addition of acid to a buffer

answer

Reacts with conjugate base and shifts equilibrium to the left, removing the H+ ions

question

Addition of alkali to a buffer

answer

Reacts with H+ ions to form water, shifting the equilibrium to the right to restore the H+ ions that have reacted

question

Buffer solution ingredients

answer

Weak acid and its salt or weak acid and aqueous alkali

question

Strength of base

answer

measure of its dissociation to form OH- ions

question

Kw

answer

1x10-14

question

Indices of H+ and OH-

answer

Add up to -14

question

pH of neutrality

answer

7

question

Weak acid calculation assumptions

answer

H+ is less than HA. H+ is equal to A-, so equal H+2. As few HA molecules have dissociates, HA concentration is the same as it was before dissociation.

question

Low pH

answer

Large H+ concentration

question

High pH

answer

Small H+ concentration

question

Each whole number pH value

answer

is a factor of 10

question

Hydronium ions

answer

H3O+; dative covalent bond between proton and lone pair on oxygen

question

Ionic equations

answer

Solid ionic compounds are shown undissociated, Cancel out species that do not change.

question

Acid and carbonate

answer

Salt, carbon dioxide and water

question

Acid and base/ alkali

answer

Salt and water

question

Acid and metal

answer

Salt and hydrogen

question

Changes in concentration during equilibrium

answer

Concentrations in Kc equation gives a different ratio. Equilibrium position must shift to restore ratio back to original Kc value.

question

Increase on bottom of Kc and decrease on top

answer

Shifts from right to left

question

Increase on top of Kc and decrease on bottom

answer

Shifts from left to right

question

Changes in pressure during equilibrium on Kc

answer

Pressure increase will increase concentrations of both reactants and products. It mostly increases the side with greater number of molecules. This changes the ratio of concentrations on the Kc equation so changes the value of Kc. Equilibrium shifts position to restore ratio back to original Kc value.

question

How catalysts affect Kc

answer

THEY DON'T, but they increase the rate of the forward and backward reaction.

question

Equilibrium constant Kc

answer

Large value; reaction is product favoured; equilibrium lies to the right. Endothermic forward reaction; increase in temperature increases Kc. Exothermic forward reaction; increase in temperature decreases Kc. Kc equation can be written from balanced equation.

question

Rate constant k

answer

Large value; fast rate of reaction. Increases with an increase in temperature because this increases the reaction rate. Can only be found from experimental data that shows the rate determining step.

question

Compromising Kc and k

answer

k must be large enough to have an efficient reaction but Kc must be large enough to be product favoured.

question

Temperature increase on an exothermic reaction

answer

Kc decreases, equilibrium shifts left and becomes reactant favoured

question

Temperature increase on an endothermic reaction

answer

Kc increases, equilibrium shifts right and becomes product favoured

question

Kc value of 1

answer

equilibrium is half way between reactants and products

question

Kc value of more than 1

answer

Reactant is product favoured and products on the right hand side of the equation are predominant at equilibrium

question

Kc value of less than 1

answer

Reactant is reactant favoured and reactants on the left hand side of the equation are predominant at equilibrium

question

Kc equation

answer

Concentration of products/ concentration of reactants

question

Dynamic equilibrium

answer

Forward and reverse reaction take place at the same rate. Concentration of reactants and products are constant.

question

Units of Kc

answer

Cancel out moldm-3

question

Powers in the rate equation show

answer

Number of molecules of this species reacting in the rate determining step

question

When the temperature is increased by 10 degrees

answer

The rate doubles; more particles are able to exceed activation energy

question

Zero order rate concentration graph

answer

Horizontal line

question

First order rate concentration graph

answer

Upward diagonal line

question

Second order rate concentration graph

answer

Upward curve line

question

Determining initial rates from concentration time graphs

answer

Draw tangent at t=0 and find the gradient of this tangent

question

Clock reactions

answer

Show the time for a certain amount of a product to be formed, show visual change such as formation of a PRECIPITATE, disappearance of a SOLID or a change in COLOUR.

question

Initial rate is proportional to

answer

1/t

question

Zero order concentration time graphs

answer

Downward diagonal line

question

Zero order half life

answer

Decreases with time

question

First order concentration time graphs

answer

Gentle downward curve

question

First order half life

answer

Constant; exponential decay

question

Second order concentration time graphs

answer

Steep downward curve

question

First half life

answer

measured from 0

question

Second half life

answer

Measured from 0-first half life

question

Units of rate constant

answer

Cancel down from moldm-3 for reactants, moldm-3s-1 for rate

question

Overall order

answer

Sum of the individual orders

question

Affect of concentration on rate

answer

Greater concentration; more collisions per second; faster reaction

question

Rate as reaction proceeds

answer

Decreases as concentrations of reactants decrease; fewer collisions per second

question

Calculating rate from concentration time graphs

answer

Draw a tangent to the curve and measure its gradient

question

Buffers are most effective when

answer

pH=pKa+/-1

question

Hydration enthalpies are always

answer

Exothermic

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