Edexcel AS Chemistry: 4th June 08

Why does Berylium have a higher ionisation energy than boron?
OMG i so failed

around 45

i wrote something about Berylium having full 2s orbitals whereas boron has 1 electron in the 2p1 orbital so its unstable and electrons can be removed easily?
i failed aswell lets just hope they lower the grade boundaries

what does strength of ionic bond depend on?
I wrote the polarising power of the cation and the polarisilbility of the anion

I got -212Kjmol^-1
And for the deflection it's ion's mass and charge.

RAINBOW, this is not a mark scheme, but i'll tell you everything i wrote (note, clearly there are things i got wrong!)

1. State the materials from which the anode and cathode are made.
Anode- titanium
Cathode- nickel (though you can also say steel)


Write the ionic half-equations for the reactions at the anode and at the cathode.
Anode- 2Cl- --> Cl2 + 2e-
Cathode- 2H+ +2e- ---> H2

Write the overall ionic equation for this process.
2NaCl + 2H20 ---> 2NaOH + H2 + Cl2

State ONE major use of chlorine
I said manufacture of hydrochloric acid

Cl2 + 2NaOH → NaOCl + NaCl + H2O
(i) Complete the following, for the reaction above:

Species oxidised ..Chlorine..... Oxidation product .....NaOCl............
Species reduced ........Chlorine........ Reduction product ........NaCl............


Calculate the minimum volume of chlorine required to produce a solution
containing 100 g of sodium chlorate(I).

im not going to do the calculation, but i think i got something like 32 or 36 dm cubed.


Define the term standard enthalpy of combustion.

The enthalpy change when one mole of a substance is completely burnt in oxygen under standard conditions of 298K and 100kPa

In the second stage of the manufacture of sulphuric acid, sulphur dioxide is oxidised
to sulphur trioxide as shown in the following equation:
2SO2(g) + O2(g) �� 2SO3(g) ΔH = –196 kJ mol–1
(i) State the temperature and pressure used for this reaction and identify the
catalyst.
Temperature .............450 degrees celcius.................................
Pressure .......................1- 4 atm..................
Catalyst ........................Pellets of Vanadium (V) oxide....


Explain, in terms of collision theory, why the rate of a reaction is increased by
increasing the temperature and by the addition of a catalyst.
Temperature
When molecules are suplied with heat they increase their ke
This means that there will me more collisions
Therefore more collisions occur at the correct angle/orientation.
A greater proportion of the molecules now have and energy > energy of activation
Therefore more collisions occur at the correct speed
Therefore increassed rate


Catalyst

A catalyst provides an alternative route for the reaction with a lower energy of activation, Thus a greater proportion of the molecules have sufficient energy to overcome the new energy of activation and react.
Therefore increased rate


State and explain the effect, if any, of increasing the temperature on the
equilibrium yield of sulphur trioxide.

Yield decreased because forward reaction is exothermic so by Le Chatelier's Principle the equilibrium shifts in the endothermic direction.

State and explain the effect, if any, of an increased pressure on the equilibrium
yield of sulphur trioxide.

Increased yield because there are 3 moles on the left and 2 moles on the right so the equilibrium shifts in the direction of less moles to oppose the changes imposed on it.


Use the data below to calculate the enthalpy change for this reaction.

You use delta H = sum of standard enthalpies of formation of the Products - sum of standard enthalpies of formation of the reactants.

you get -1056 kJ per mol

State ONE large-scale use of sulphuric acid.
Acid used in car batteries
(can also say fertilizers, paints and dyes, plastics, soaps and detergents..)


State TWO features that members of a homologous series have in common.
They have the same functional group
They have similar chemical properties
The show a gradual change in physical properties
A mention of the homologous increment


Name the homologous series to which propene belongs.
Alkenes

Propene can be converted into a mixture of 2-chloropropane (as the major
product) and 1-chloropropane.
Classify the reaction involved and identify the reagent required.
Classification ...........Electrophilic addition........................
Reagent ..........Hydrogen chloride in the gas phase......


1-chloropropane can be converted into butanenitrile, CH3 CH2CH2CN.
Classify the reaction involved. Identify the reagent required and state ONE
essential condition.
Classification ...........Nucleophilic substitution....................................
Reagent .........Potassium Cyanide.......................
Condition .....Heat under reflux with potassium cyanide dissolved in ethanol............


Define the term structural isomers.

Molecules that have the same molecular formula but different structural formulae.


Draw the full structural formula of any structural isomer of butanenitrile, showing
all the bonds.

Cant draw it here, but there is a triple covalent cond connecting the C to the N


1-chloropropane and 1-bromopropane both react with ammonia to give
1-propylamine.
State and explain, in terms of bonding and kinetics, which of 1-chloropropane and
1-bromopropane would react faster with ammonia.


Bromopropane becase the Br-C bond is longer therefore weaker therefore less energy is required to break the bond, therefore faster.


1-chloropropene, CH3CH=CHCl, can be polymerised to form poly(1-chloropropene).
Draw the repeat unit of poly(1-chloropropene).

You know this



Explain why 1-chloropropene exists as two different geometric isomers, but propene
does not.
Two essential conditions are required for two molecules to exist as geometric isomers:
1. Double bond- both molecules satisfy this condition
2. The carbon atoms must be attached to DIFFERENT atoms/groups of atoms.
Propene doesnt satisfy this condition



Consider the following series of reactions.
reaction 1 reaction 2
CH2=CH2 ---> CH2OHCH2OH ----> CH2BrCH2Br
Ethene Compound A Compound B

(i) Identify the reagent required for reaction 1.
Potassium Manganate

Name compound B.
ethan-1,2-diol?? (i honestly dont remember what i put down for this one!)

(iii) Identify the TWO reagents required for reaction 2.

Potassium promide and concentrated sulphuric acid


Compound A can be oxidised by heating with an acidified solution of potassium
dichromate(VI).
Give the colour change that would be observed and draw the full structural
formulae of TWO possible oxidation products, showing all bonds.
Colour from .....orange....... to .........green..
Oxidation products

an aldehyde and a carboxylic acid
(cant draw them!)



Suggest the name or formula of a compound that would be obtained if
compound B were reacted with ethanolic potassium hydroxide.
i said ethene


Compound B can be produced by reacting ethane with bromine in the presence
of ultra-violet light.
Suggest why a good yield of compound B would not be obtained and identify
another organic product that would be formed during the reaction.

This reaction involves the homolytic fission of a halogen gas. The free radicals produced then subrtitute the hydrogen atoms on the alkane molecule. This is a continuous and random process, so it is impossible to tell which haloalkane will be produced.
Other product: eg. tetrabromoethane.


Write an equation for the complete combustion of ethane.
gives carbon dioxide and water (then balance)

iii) Define the term empirical formula.
the simplest ratio of the atoms in a molecule

Give the empirical formula for ethane.
CH2

Give the formula of an alkane, containing more than one carbon atom, whose
molecular and empirical formulae are the same.

C3H8