MC test: Covalent structures (1)

Multiple choice test on 4.3 Covalent structures (1)

Use the following 'quiz' to test your knowledge and understanding of this sub-topic. You will need access to a periodic table (Section 6 of the IB data booklet).

If you get an answer wrong, read through the explanation carefully to learn from your mistakes.

Which are correct ways of showing the Lewis structure of ammonia?

Lewis structures can be shown using dots or crosses to represent electrons, or a line to represent a pair of electrons or any combination of these. The IB accepts all the three shown and also .

 

Which is the Lewis structure of ethanol?

The Lewis structure must show all the pairs of valence electrons - bonding and non-bonding.

 

Which species can be described using three resonance structures?

All of them can be described using two resonance structures except the nitrate ion 

 

Which are allotropes of carbon?

I. graphite

II. buckminsterfullerene

III. diamond

Buckminsterfullerene, C60 is the correct name for "Bucky ball". It was first generated in 1985 and occurs in small quantities in soot.

 

Which compound contains a coordinate (dative) covalent bond?

 

Which best explains why graphite conducts electricity?

Graphite consists of three strong bonds between C atoms in the hexagonal rings and one weak bond holding the layers together. The electrons in this weak bond are delocalized and so can conduct electricity.

 

Which compound does not obey the 'octet' rule?

BCl3 only has six electrons around the central boron atom.

 

Which compound has an expanded 'octet'?

SF6 has twelve electrons around the central sulfur atom. (Note that although some other sulfur compounds, such as SO2 and SO3, can be drawn with an expanded octet they can also be drawn following the octet rule by using resonance structures - this is not possible with SF6.)

 

Which pure substance will have the lowest melting point?

Although sodium chloride is ionic and melts at 801 oC the other three substances all have giant molecular structures and have much higher melting points as a considerable amount of  energy is required to break down all the strong covalent bonds holding the structures together.

 

Which statements are true concerning graphene?

I. Graphene is an allotrope of carbon

II. Graphene consists of a single layer made up of carbon atoms arranged in hexagonal rings

III. Weight for weight graphene is nearly as strong as steel

Weight for weight graphene is about 200 times stronger than the strongest steel.

 

Total Score:
All materials on this website are for the exclusive use of teachers and students at subscribing schools for the period of their subscription. Any unauthorised copying or posting of materials on other websites is an infringement of our copyright and could result in your account being blocked and legal action being taken against you.