A-LevelChemistryGroup 179701/22 · May/June 2019 · Q211 Marks

Group 17 elements are commonly referred to as the halogens.

(a)State and explain the trend in volatility of chlorine, bromine and iodine down the group.[3]
(b)(i)State the conditions required for chlorine to react with hydrogen at room temperature.[1]
(b)(ii)On heating, iodine reacts with hydrogen in a reversible reaction. Give the equation for this reaction. Include state symbols.[2]
(c)Hydrogen chloride reacts with water. HCl + H2O → H3O+ + Cl⁻
(c)(i)In this reaction, one of the reactants behaves as a Brønsted-Lowry acid. What is meant by the term Brønsted-Lowry acid?[1]
(c)(ii)Identify the reactant behaving as an acid and its conjugate base. acid .......................... conjugate base ..........................[1]
(c)(iii)Name the type of bond formed between H⁺ and H₂O to make H₃O⁺.[1]
(c)(iv)For H₃O⁺, predict its shape and the H–O–H bond angle. shape .......................... bond angle ..........................[2]

Mark scheme

Marking points from the official mark scheme (May/June 2019). The mark or mark type is shown in brackets.

[1] decrease (in volatility)
[1] increasing (strength of) induced dipole (id) (interactions between molecules)
[1] increasing number of electrons
[1] ultra-violet / uv
[1] M1 correctly balanced equation
[1] M2 correct state symbols AND use of equilibrium sign
I2 (g/s) + H2(g) <=> 2HI (g)
[1] proton / H⁺ donor
[1] acid HCl AND conjugate base Cl⁻
[1] co-ordinate / dative (covalent)
[1] (triangular / trigonal) pyramid(al)
[1] 107(°)

On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.