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Date May 2018 Marks available 1 Reference code 18M.2.hl.TZ1.6
Level HL Paper 2 Time zone TZ1
Command term Annotate Question number 6 Adapted from N/A

Question

The diagram shows an incomplete voltaic cell with a light bulb in the circuit.

Identify the missing component of the cell and its function.

[2]
a.

Deduce the half-equations for the reaction at each electrode when current flows.

 

[2]
b.

Annotate the diagram with the location and direction of electron movement when current flows.

[1]
c.

Calculate the cell potential, in V, using section 24 of the data booklet.

[1]
d.

Determine the loss in mass of one electrode if the mass of the other electrode increases by 0.10 g.

[2]
e.

Markscheme

salt bridge

 

movement of ions

OR

balance charge

 

Do not accept “to complete circuit” unless ion movement is mentioned for M2.

[2 marks]

a.

Positive electrode (cathode):

Ag+(aq) + e → Ag(s)

 

Negative electrode (anode):

Mg(s) → Mg2+(aq) + 2e

 

Award [1 max] if correct equations given at wrong electrodes.

[2 marks]

b.

in external wire from left to right

[1 mark]

c.

«E = +0.80 V – (–2.37 V) = +» 3.17 «V»

[1 mark]

d.

«moles of silver 0.10  g 107.87  g mo l 1 »

moles of magnesium  = 0.5 × 0.10   g 107.87   g mo l 1

«loss in mass of magnesium  = 24.31  g mol × 0.5 × 0.10  g 107.87  g mo l 1 = » 0.011 «g»

 

Award [2] for correct final answer.

[2 marks]

e.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.
[N/A]
d.
[N/A]
e.

Syllabus sections

Core » Topic 9: Redox processes » 9.2 Electrochemical cells
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