MCQs for Chapters 3 and 4

The diagram shows the structure of boron nitride which is similar to that of graphite. Which property is this compound likely to have?

• It acts as a lubricant.

• It is soluble in water.

• It has a low melting point.

• It is transparent when pure.

The table shows the number of neutrons and electrons in four particles. Which two particles are isotopes?

• E and G

• E and J

• E and L

• L and J

An element Z has the electronic configuration 2.8.4. Which of the following best describes the compound formed between Z and hydrogen?

• A solid non-electrolyte.

• A colourless gas that dissolves in water to form a solution that conducts an electric current.

• A colourless gas that dissolves in organic solvents to form a non-conducting solution.

• A solid that conducts an electric current when molten.

Answer explanation

Z is clearly the atom of silicon. With hydrogen, it forms covalent bonds by sharing its valence electrons. This forms a hydride, which is a simple molecule. Most simple molecules are soluble in organic solvents and insoluble in water. The solution it forms does not have any mobile ions to carry electrical charges. Hence, it is non-conducting. SiH4 is silane, a colourless, flammable, toxic gas with a repulsive odour. It is a strong irritant to skin, eyes and mucous membranes.

Some physical properties of four solids I - IV are given. What are the identities of these four solids?

• I - sodium, II - diamond, III - iodine, IV - magnesium chloride

• I - sodium, II - magnesium chloride, III - sodium, IV - iodine

• I - magnesium chloride, II - diamond, III - sodium, IV - iodine

• I - magnesium chloride, II - diamond, III - iodine, IV - sodium

Which substance conduct electricity by movement of electrons?

• molten magnesium chloride

• ethanol

• graphite

• solid sodium chloride

Answer explanation

In graphite, there is a delocalized electron on each carbon atom. These electrons, when mobile, flow along the layers and thus constitute what we call an electric current.

The electronic structures of four atoms are shown. Which atom(s) is/are chemically unreactive?

• 1 only

• 3 only

• 1 and 3 only

• 2 and 4 only

The diagrams show the structures of two forms of carbon, T and S. Which set of data is correct for these two structures?

• conducts electricity - T, very hard material - S, can be used as a lubricant - none

• conducts electricity - S, very hard material - T, can be used as a lubricant - S

• conducts electricity - S, very hard material - T, can be used as a lubricant - none

• conducts electricity - T, very hard material - S, can be used as a lubricant - T

• covalent only

• covalent and ionic only

• ionic and metallic only

• metallic and covalent only

• aluminium oxide

• diamond

• graphite

• sodium chloride

Which diagram best shows the structure of an alloy?

• 
• 
• 
•