TOPIC 3 AND 4

P, Q and R represent three different structures of an element. Which structures are giant molecular?

• P, Q and R

• P and Q only

• P and R only

• Q and R only

A sample of gas occupies 240 cm³ at 37 °C and 100 kPa. How many moles of gas are present in the sample?

• 9.32 × 10^–6

• 9.32 × 10^–3

• 0.0781

• 78.1

The eight species that follow all have covalent bonds. In which pair do the species have different shapes from each other?

• BeCl₂ and CO₂

• CH₄ and NH⁺₄

• NH₃ and BF ₃

• SCl₂ and H₂O

Which pair of substances are both simple molecular?

• C₆₀ and graphene

• C₆₀ and iodine

• graphene and graphite

• graphite and iodine

Element W is in period three of the Periodic Table and has a solid, white oxide, X.

X is thermally stable and has a very high melting point.X is slightly soluble in water.Which row describes the structure and bonding of X?

• A

• B

• C

• D

Ethane, CH₃CH₃, and fluoromethane, CH₃F, have the same number of electrons in their molecules. Their boiling points are given. What is responsible for this difference in boiling points?

• CH₃F has a larger Mr than CH₃CH₃

• CH₃F has a permanent dipole, CH₃CH₃ does not

• CH₃F has a strong C–F bond, CH₃CH₃ does not

• Hydrogen bonding occurs in CH₃F, but not in CH₃CH₃

What changes in conditions or molecular properties make it more likely that gases approach ideal behaviour?

• higher pressure

• lower temperature

• more polar molecules

• weaker intermolecular forces

In this question you should assume the vapour behaves as an ideal gas. 0.175 g of a volatile liquid produces a vapour of volume 4.50 × 10^–5 m³ at 100 °C and pressure of 1.013 × 10⁵ Pa. What is the Mr of the liquid?

• 31.9

• 87.1

• 119

• 127

Which molecule does not have any 90° or 180° bond angles?

• C₂H₆

• CO₂

• PF₅

• SF₆

A stable ion N₅⁺ has been produced by research chemists. Which structure is most likely to show the electron arrangement of this ion?

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