OCR A Level Chemistry B (Salters) Practical skills in chemistry June 2022 question paper H433/03

This question is about haloalkanes and their reactivity.

Haloalkanes are useful intermediates for preparing a range of organic compounds.

A flowchart showing the synthesis of three organic compounds is shown below.

Complete the flowchart showing the structures of compounds A and C.

On the dotted line show the reagent needed to form compound B.

Which homologous series does compound B belong to?

Some haloalkanes act as greenhouse gases that absorb infrared radiation in the troposphere.

Give the source of this infrared radiation.

This question is about the enthalpy change of the reaction of zinc with copper(II) sulfate solution.

A student investigates the temperature change when Reaction 2.1 occurs.

The student adds 1.20 g of powdered zinc to 50.0 cm³ of 0.200 mol dm^–3 copper(II) (i) sulfate solution in a glass beaker.

Use calculations to show which is the limiting reagent.

limiting reagent is........

Calculate _rH for Reaction 2.1 using the data shown below.

	fHo / kJ mol–1
Cu2+(aq)	+ 64.4
Zn2+(aq)	–152.4

This question is about redox and electrochemical cells.

Table 3.1 shows standard electrode potentials, some of which will be needed for the rest of this question.

The reaction between zinc metal and aqueous Cu²⁺ ions can be arranged in a cell to (a) produce electrical energy.

A diagram of a copper/zinc cell is shown in Fig. 3.1.

copper half-cell
zinc half-cell

Fig. 3.1

When the cell delivers a current, oxidation takes place in one half-cell and reduction in the other.

Write half-equations for the reactions that take place in each half-cell.

Show state symbols.

oxidation reaction:

reduction reaction:

Explain the purpose of the salt bridge.

Calculate E _cell for the copper/zinc cell in Fig. 3.1.

Standard electrode potentials can be used to decide whether a reaction is feasible.

Predict, with reasons, if any reaction could take place in each of the following situations.

Use the data in Table 3.1.

Metallic silver is added to aqueous iron(II) sulfate.

Aqueous potassium chloride is added to acidified potassium manganate(VII) solution.

The relationship between the ion concentration and the electrode potential for a metal/ion electrode is given (at 298 K) by Equation 3.1, where n is the number of electrons transferred in the half reaction.

Explain how Equation 3.1 shows that E = E under standard conditions.

Calculate the electrode potential of a Zn²⁺(aq) / Zn(s) half-cell when (ii) [Zn²⁺(aq)] = 0.20 mol dm^–3.

This question refers to the Practical Insert that is provided as an insert to this paper.

Suggest how the students accurately made up a solution of 0.300 mol dm^–3 copper(II) nitrate (a) from their standard 0.400 mol dm^–3 solution.

Name the apparatus involved.

Use your graph on page 12 and data from the insert to calculate the percentage by mass of copper in the brass sample.

A copper(II) ion is said to form an octahedral complex with water ligands.

Explain the term ligand.

Complete the diagram below to show the shape of the octahedral copper(II) complex ion with water ligands.

d-block elements form a variety of differently coloured complex ions.

Explain, in terms of electronic structure, why these complex ions are coloured and why different complexes of the same cation have different colours.