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OCR A Level Chemistry B (Salters)H433/03 Practical skills in chemistry MERGED QUESTION PAPER AND MARK SCHEME FOR JUNE 2024 $11.99   Add to cart

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OCR A Level Chemistry B (Salters)H433/03 Practical skills in chemistry MERGED QUESTION PAPER AND MARK SCHEME FOR JUNE 2024

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OCR A Level Chemistry B (Salters)H433/03 Practical skills in chemistry MERGED QUESTION PAPER AND MARK SCHEME FOR JUNE 2024

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  • November 5, 2024
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  • 2024/2025
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Friday 21 June 2024 – Morning
A Level Chemistry B (Salters)
H433/03 Practical skills in chemistry
Time allowed: 1 hour 30 minutes

, 2
1 This question is about electrochemical cells.

Table 1.1 shows some standard electrode potentials.

Table 1.1

Half-reaction Eo/V
Zn2+(aq) + 2e– Zn(s) –0.76
Fe2+(aq) + 2e– Fe(s) –0.44
Pb2+(aq) + 2e– Pb(s) –0.13
Cu2+(aq) + 2e– Cu(s) +0.34
Ag2O(s) + H2O(l) + 2e– 2Ag(s) + 2OH–(aq) +0.34
Fe3+(aq) + e– Fe2+(aq) +0.77
Ag+(aq) + e– Ag(s) +0.80
Cl 2(aq) + 2e– 2Cl –(aq) +1.36

(a) The values in Table 1.1 are described as standard electrode potentials.

(i) Name the electrode against which these values are measured.

..................................................................................................................................................... [1]

(ii) What are the standard conditions at which these standard electrode potentials are measured?

..........................................................................................................................................................

..................................................................................................................................................... [2]

(b)
(i) Some students set up the cell below. The cell consists of a copper/copper ion half-cell and a
lead/lead ion half-cell. The left-hand electrode is negative.

– +
V


................................ salt bridge ................................




................................ ................................

Identify the metals and ions by labelling the diagram with element symbols and ion formulae.
Include state symbols. [2]

© OCR 2024

, 3
(ii) Suggest how the students make the salt bridge.

..........................................................................................................................................................

..................................................................................................................................................... [1]

(iii) Use Table 1.1 to calculate E o for the cell.

E o cell = ....................................................... V [1]

(c) ‘Button batteries’ are small cells used where there is not much space, for example, in a watch or
mobile phone.

The make-up of a silver oxide (Ag2O) button battery is shown below.

insulating seal negative electrode top cup
(–)

zinc powder in an alkaline
electrolyte encased in a
conducting steel top cup




positive electrode (+)
consisting of a silver oxide (Ag2O)
paste in a conducting steel bottom cup porous separator bottom cup



(i) Use Table 1.1 to write ion-electron half equations for the reactions happening at the negative and
positive electrodes.

Then write the equation for the overall cell reaction.

Half-equation for the negative electrode:



Half-equation for the positive electrode:



Equation for the overall cell reaction:



[3]


(ii) Suggest the purpose of the porous separator shown in the diagram.

..........................................................................................................................................................

..................................................................................................................................................... [1]
© OCR 2024 Turn over

, 4
BLANK PAGE




PLEASE DO NOT WRITE ON THIS PAGE




© OCR 2024

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