STPM Group 17

Which of the following is best explained by the relative strength of the intermolecular forces between the hydrogen halide molecules, HZ, (fluoride to iodide) in the liquid state?

• The enthalpy of formation

• The enthalpy of vaporisation

• The enthalpy of combustion

• The H-Z bond energy

The solution produced when chlorine is bubbled through dilute sodium hydroxide can be used

• As pesticide

• as bleaching agent

• in sterilising water

• to extract bromine

1. An aqueous solution of X has the following properties.

(i) Reacts with aqueous silver nitrate to form a precipitation which dissolves in aqueous ammonia.

(ii) Reacts with aqueous barium hydroxide to form salt and water.

(iii) Decomposes in the presence of sunlight to evolve a gas.

What could X be?

• HCl and NH₄Cl

• HCl and HOCl

• HBr and HOCl

• HBr and NH₄Cl

A coloured vapour which condenses to liquid is obtained when compound Q is heated with concentrated sulphuric acid. Q is

• potassium iodide

• potassium chloride

• potassium bromide

• potassium ethanedioate

The reactivity of the halogen Cl_2, Br₂ and I₂ decreases down Group 17 of the Periodic Table. Which property does not influence the trend in the reactivity of the halogens?

• Atomic size

• Electron affinity

• Ionisation energy

• Bond energy

An element X has valence electron configuration ns²np⁵ and a melting point of -7°C. AgX does not dissolve in aqueous ammonia and is used in black and white photography. Element X is most probably

• fluorine

• chlorine

• Bromine

• Iodine

Astatine is a radioactive halogen which is below iodine in the Periodic Table. Which statement about astatine is not true?

• Hydroastatic acid, Hat, is a strong acid

• Astatide ion, At^-, reduces concentrated sulphuric acid to hydrogen sulphide.

• The standard reduction potential of astatine is more positive than that of iodine.

• Astatine reacts reversibly with hydrogen at high temperature in the presence of a catalyst.

The elements in Group 17 (chlorine to iodine) of the Periodic Table are the most reactive non-metals in each of their period. Which property of the elements that increases on descending the group?

• Enthalpy of vaporisation

• Ionisation energy

• Electron affinity

• Bond energy

The halogens are important chemicals in our daily lives. Which statement about Cl₂, Br₂ and I₂ is true?

• The halogens can act as both oxidising and reducing agents

• The strength of the Van der Waals forces increases from Cl₂ to I₂.

• Cl₂, Br₂ and I₂ are formed when their respective halides react with concentrated H₂SO₄.

• Cl₂, Br₂ and I₂ react vigorously with hydrogen gas in the presence of ultraviolet light.

The reaction between chlorine and hot, concentrated sodium hydroxide produces

• ClO₃^-

• Cl^-

• H₂O