DP Chemistry (last assessment 2024)

Test builder »

Question 19N.2.sl.TZ0.5

Select a Test
Date November 2019 Marks available [Maximum mark: 13] Reference code 19N.2.sl.TZ0.5
Level sl Paper 2 Time zone TZ0
Command term Annotate, Apply, Calculate, Determine, Explain, Formulate, Show, Solve, State Question number 5 Adapted from N/A
5.
[Maximum mark: 13]
19N.2.sl.TZ0.5

Copper forms two chlorides, copper(I) chloride and copper(II) chloride.

(a(i))

State the electron configuration of the Cu+ ion.

[1]

Markscheme

[Ar] 3d10
OR
1s2 2s2 2p6 3s2 3p6 3d10 ✔

(a(ii))

Copper(II) chloride is used as a catalyst in the production of chlorine from hydrogen chloride.

4HCl (g) + O2 (g) → 2Cl2 (g) + 2H2O (g)

Calculate the standard enthalpy change, ΔHθ, in kJ, for this reaction, using section 12 of the data booklet.

[2]

Markscheme

ΔHθ = ΣΔHθf (products) − ΣΔHθf (reactants) ✔
ΔHθ = 2(−241.8 «kJ mol−1») − 4(−92.3 «kJ mol−1») = −114.4 «kJ» ✔

 

NOTE: Award [2] for correct final answer.

(a(iii))

The diagram shows the Maxwell–Boltzmann distribution and potential energy profile for the reaction without a catalyst.

Annotate both charts to show the activation energy for the catalysed reaction, using the label Ea (cat).

[2]

Markscheme

Ea (cat) to the left of Ea ✔                        

 

peak lower AND Ea (cat) smaller ✔

(a(iv))

Explain how the catalyst increases the rate of the reaction.

[2]

Markscheme

«catalyst provides an» alternative pathway ✔

«with» lower Ea
OR
higher proportion of/more particles with «kinetic» E ≥ Ea(cat) «than Ea» ✔

(b)

Solid copper(II) chloride absorbs moisture from the atmosphere to form a hydrate of formula CuCl2•xH2O.

A student heated a sample of hydrated copper(II) chloride, in order to determine the value of x. The following results were obtained:

Mass of crucible = 16.221 g
Initial mass of crucible and hydrated copper(II) chloride = 18.360 g
Final mass of crucible and anhydrous copper(II) chloride = 17.917 g

Determine the value of x.

[3]

Markscheme

mass of H2O = «18.360 g – 17.917 g =» 0.443 «g» AND mass of CuCl2 = «17.917 g – 16.221 g =» 1.696 «g» ✔

moles of H2O = «0.443 g18.02 g mol−1=» 0.0246 «mol»
OR
moles of CuCl2 =«1.696 g134.45 g mol−1= » 0.0126 «mol» ✔

«water : copper(II) chloride = 1.95 : 1»
«x =» 2 ✔

NOTE: Accept «x =» 1.95.

NOTE: Award [3] for correct final answer.

An electrolysis cell was assembled using graphite electrodes and connected as shown.

(c(i))

State how current is conducted through the wires and through the electrolyte.

Wires: 

Electrolyte:

[2]

Markscheme

Wires:
«delocalized» electrons «flow» ✔

Electrolyte:
«mobile» ions «flow» ✔

(c(ii))

Write the half-equation for the formation of gas bubbles at electrode 1.

[1]

Markscheme

2Cl− → Cl2 (g) + 2e−
OR
Cl− → 1 2 Cl2 (g) + e− ✔

NOTE: Accept e for e−.

Syllabus sections