Edexcel A Level Data Booklet

What is in the Edexcel A Level Data Booklet?

The Edexcel Advanced Level GCE in Chemistry (9CHO) data booklet is provided for you in an exam to look up data for a specific question. In this data booklet, you will find the following sections. 

• Physical constants

• Infrared spectroscopy

• Nuclear magnetic resonance

• Pauling electronegativities

• Indicators

• Standard Electrode Potentials

• The Periodic Table of the Elements

Note that the Periodic Table is the last thing in the booklet, so turn straight to the back page if you need this. You may need the Periodic Table to look up Ar’s for specific elements or to locate a specific element to write an electronic configuration. Either way, make sure you know exactly where to turn to!

Physical constants

The first section contains general physical constants which are required for calculations. Such as using the Ideal Gas equation, and calculating the number of particles or the pH of a strong base. You are not expected to know these values, but be able to locate them and use them when required. 

Source Edexcel Advanced Level GCE in Chemistry (9CH0) Data Booklet

Infrared spectroscopy

Infrared (IR) spectroscopy is a technique used to identify compounds based on changes in vibrations of atoms when they absorb IR of certain frequencies. 

Particular absorbance have characteristic widths (broad or sharp) and intensities (strong or weak). For example, hydrogen bonds cause the O-H bonds in alcohols and carboxylic acids to be broad whereas the C-O bond in carbonyl (C=O) groups have a strong, sharp absorbance peak

On a typical IR spectrum, percentage transmittance is plotted against the wavenumber range in cm-1. This tells us how many wavelengths fit into 1 cm3. The energies absorbed by different functional groups are given as a range and an unknown compound can be identified by comparing its IR spectrum to the IR spectrum of a known compound.

So, if we analyse a compound, we can see specific peaks for different bonds. When asked to identify a particular bond within a compound, watch out for the type of compound. For example, O-H bonds have a different characteristic absorption range in alcohols and carboxylic acids. In alcohols and phenols, the O-H bond has an absorption range of 3750 - 3200 and in carboxylic acids, the absorption range is 3300 - 2500. 

An example Edexcel A Level chemistry question is: 

Source AS Level Paper 2 8CH0/02 Jun / Nov 2021

Source AS Level Paper 2 8CH0/02 Jun / Nov 2021

The oxidation of cyclohexanol will form a ketone, so the O-H bond stretching 3750 – 3200 cm-¹ in cyclohexanol is not present in cyclohexanone and therefore the C=O bond stretching 1720 – 1700 cm-¹ appears in cyclohexanone.

Make sure you do not get muddled up with the next section during an exam, double check you are reading the data from the correct table!

Nuclear magnetic resonance

Nuclear Magnetic Resonance (NMR) spectroscopy is used for analysing organic compounds. NMR spectra show the intensity of each peak against their chemical shift. All samples are measured against a reference compound – Tetramethylsilane (TMS). There are two different types of nuclear magnetic resonance. This has a value of zero. 

1H nuclear magnetic resonance

The area under each peak gives information about the number of protons in a particular environment and The height of each peak shows the intensity / absorption from protons. The position of each peak in the spectrum (chemical shift) provides information about the electronic environment of the atoms. Different functional groups and types of atoms have characteristic chemical shifts. These can be read from the table. 

13C nuclear magnetic resonance

The data you are given is as follows:

Source Edexcel Advanced Level GCE in Chemistry (9CH0) Data Booklet

The same idea can be applied to the 13C nuclear magnetic resonance (NMR) table as with 1H NMR. Atoms with odd mass numbers usually show signals on NMR. For example, isotopes of atoms; many of the carbon atoms on organic molecules are carbon-12. A small quantity of organic molecules will contain the isotope carbon-13 atoms and these will show signals on a 13C NMR. The magnetic field strengths of carbon-13 atoms in organic compounds are measured and recorded on a spectrum and non-equivalent carbon atoms appear as peaks with different chemical shifts. 

The values are not given in a traditional table style so take your time to identify the correct chemical shift and read from the horizontal axis. And remember the values increase from right to left! 

Pauling electronegativities

Electronegativity is the ability of an atom to attract a pair of electrons in a covalent bond towards itself. We can measure electronegativity by using the Pauling scale. The Pauling electronegativity values range from 0.7 to 4, with caesium being the least electronegative with a value of 0.7 and fluorine being the most electronegative with a value of 4.0. 

Electronegativity generally increases across a period from left to right on the periodic table and decreases down a group. Fluorine, being the most electronegative element, has the highest electronegativity value. 

You are provided with these values as you could be asked to justify why a covalent bond does or does not exhibit polarity or explain the type of bonding. When the electronegativity difference between two atoms is large, an ionic bond is more likely to form, with one atom donating electrons to the other. 

For a covalent bond, if there is a difference in electronegativity the bond will be polar. The C-F bond is polar as carbon has a value of 2.5 and fluorine has a value of 4.0. A C-H bond is not electronegative as hydrogen has a value of 2.1. This is not a significant difference for the bond to exhibit electronegativity. 

Indicators

An acid base indicator is a weak acid which dissociates to give an anion of a different colour depending on the pH. These are used in titration curves

Around the equivalence point of a titration, the pH changes very rapidly. Indicators change colour over a narrow pH range approximately centred around the pKa of the indicator. An indicator will be appropriate for a titration if the pH range of the indicator falls within the rapid pH change for that titration.

A likely question is being asked to choose a suitable indicator for a titration. A suitable indicator should change colour close to the endpoint for that specific titration, but these are not always the same. For a strong acid strong base titration the equivalence point is at pH 7, for a strong acid weak base it is below pH 7 and for a strong base weak acid titration it is above 7. Therefore you have to choose the indicator that will change colour in the correct range. For example, phenolphthalein will change colour over a range of pH of 8.2 to 10.0 so will be suitable for a strong base weak acid titration. Note that the colour change for phenolphthalein in ethanol is colourless in acid to red in alkaline conditions, though pink is also accepted in this course. For more information on indicators see our revision note on titration curves.

Standard Electrode Potentials

The E^Θ values of a species indicate how easily they can be oxidised or reduced and as are written as reduction reactions as standard, so they gain electrons.
Mg²+ (aq) + 2e- ⇌ Mg (s)     E^θ = -2.37
2Br - (aq) + 2e- ⇌ Br₂ (s)     E^θ = +1.09
The more positive the value, the easier it is to reduce the species on the left of the half-equation. The reaction will tend to proceed in the forward direction. So bromide ions are more likely to form a bromine molecule.

The less positive the value, the easier it is to oxidise the species on the right of the half-equation. The reaction will tend to proceed in the backward direction. So magnesium metal is more likely to form magnesium ions.

All values are measured at an ion concentration of 1.00 mol dm-³ a temperature of 298 K  and a pressure of 100 kPa using a standard hydrogen electrode

Source SaveMyExams 6.1.2 Standard Electrode Potential Revision Note

The Periodic Table of the Elements

Periodicity is the study of trends that occur in the Periodic Table. There are a number of trends that you need to be able to explain in Edexcel A Level Chemistry which occur down a group and across a period. These include melting and boiling points, structure and bonding, atomic radius and ionisation energy. If you are asked a question that involves explaining these trends, always have the Periodic Table to hand. You can then check where the elements are in relation to one another, or even annotate the table in the data booklet. You may even want to note that electronegativity increases from left to right and decreases down the groups.

For Edexcel Advanced Level Chemistry, the values for the relative atomic mass, Ar, are given to 1 decimal place and the data is arranged as shown. Note that the relative atomic mass is the number on the top and the proton number is the number on the bottom.

Source Edexcel Advanced Level GCE in Chemistry (9CH0) Data Booklet

This is vital to show in your answers, so when calculating the M_r of a compound such as MgCO₃, you should include:
(1 x Mg) + (1 x C) + (3 x O) 
(1 x 24.3) + (1 x 12.0) + (3 x 16.0) = 84.3 

If you do not include the decimal place you will lose the mark.