W2 Sept C-S4D Pure Chem O Level Rev 1

Chromatography was carried out on 6 different samples, numbered 1 to 6. The diagram below shows the results of separation into their components:

Which of the following statements are false?

• Substance 2 can be found in substance 5.

• Substances 3 and 6 both contain at least one identical component.

• There are two pure substances and four mixtures.

• There are two substances that contain identical components.

The following diagram shows the structure of graphene, an allotrope of carbon. The carbon atoms are arranged in a honeycomb lattice.

Which of the following rows shows the likely properties of graphene?

• A

• B

• C

• D

How many electrons are shared between the atoms in one molecule of ethane, and one molecule of nitrogen?

• ethane: 6, nitrogen: 2

• ethane: 7, nitrogen: 6

• ethane: 8, nitrogen: 4

• ethane: 14, nitrogen: 6

Zirconium(IV) oxide can be used to make synthetic diamonds, and industrial cutting tools. It has a melting point of 2715 ^oC and a boiling point of 4300 ^oC. 

Explain in terms of structure and bonding, why the melting point of zirconium(IV) oxide is very high.

The structures of diamond and graphite are shown below.

Identify the type of strong bonds present in diamond and graphite.

The structures of diamond and graphite are shown below.

State whether graphite and diamond have high or low melting points. Explain your answer using the structure and bonding present.