Structure (Edexcel A Level Chemistry)

This question is about methanol, CH₃OH.

Draw a dot-and-cross diagram to show the bonding in a molecule of methanol.

Show outer shell electrons only.

Predict which bond has the shortest bond length in a molecule of methanol.

Methanol is soluble in water.

(1)

(3)

This question is about some halogens and their compounds.

The intermolecular attractions between halogen molecules are London forces.

A student carries out experiments to determine the order of reactivity of three halogens:
bromine, chlorine and iodine.
The student is provided with aqueous solutions of the following five substances:

• bromine
• iodine
• potassium chloride
• potassium bromide
• potassium iodide.

The student has no access to chlorine gas or chlorine water.
The student uses cyclohexane, an organic solvent, to identify the halogen present at the end of each experiment.

The student carries out the smallest number of experiments required to determine the order of reactivity of the halogens.

Describe the experiments and the expected observations.

Include in your answer ionic equations for any reactions that occur.

State symbols are not required.

This question is about compounds of Group 5 elements.  

Phosphorus forms two chlorides with the formulae PCl₃ and PCI₅. 

(3)

(3)

(2)

Nitrogen trichloride, NCl₃, has a boiling temperature of 344 K, and nitrogen trifluoride, NF₃, has a boiling temperature of 144 K.

Explain this difference in boiling temperatures, by referring to all the intermolecular forces present.  

Which of these compounds produces hydrogen chloride when it reacts with PCl₅? 

Compound X is a component of synthetic oils used as lubricants, for instance in the gearboxes of ships.

Name the three functional groups present in compound X.

The effectiveness of this synthetic oil is much reduced if it is contaminated with water.

Give, in terms of a chemical reaction, a possible reason for this.

An alternative to synthetic oil is known as mineral oil and consists solely of hydrocarbons separated from crude oil.

This question is about the solubility of some alcohols.
The table shows the solubility in water of the first six alcohols in a homologous series.

State what is meant by a homologous series.

You may use the alcohols in the table to illustrate your answer.

Explain why methanol and water are ‘soluble in all proportions’.

You must include a diagram in your answer.

The compounds hydrogen fluoride, water and methane, all have simple molecular structures, but they have significantly different boiling temperatures.

Discuss the reasons for the differences in the boiling temperatures of the three compounds, using the data in the table and the Pauling electronegativity values in the Data Booklet.

The table shows some information about a selection of elements and compounds.

Explain the difference in the melting temperatures of magnesium oxide and potassium bromide.

Explain why the electrical conductivity of solid potassium bromide is poor but an aqueous solution of potassium bromide is a good electrical conductor.

Graphene, graphite and diamond are all forms of solid carbon.
Explain, in terms of structure and bonding, why graphene and graphite are good electrical conductors but diamond is a poor electrical conductor.

You may include labelled diagrams in your answer.

Deduce two possible reasons why the density of iron (7.86 g cm⁻³) is much greater than the density of graphite (2.2 to 2.8 g cm⁻³).

The compressive strength is a measure of the energy required to break some of the bonds within a substance.

Deduce possible reasons why there are two widely different values for the compressive strength of graphite.
Both the values (2.3 and 15.3 GPa) are valid experimental results.