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Date May 2018 Marks available 1 Reference code 18M.2.hl.TZ2.3
Level HL Paper 2 Time zone TZ2
Command term Deduce Question number 3 Adapted from N/A

Question

The emission spectrum of an element can be used to identify it.

Hydrogen spectral data give the frequency of 3.28 × 1015 s−1 for its convergence limit.

Calculate the ionization energy, in J, for a single atom of hydrogen using sections 1 and 2 of the data booklet.

[1]
a.iii.

Calculate the wavelength, in m, for the electron transition corresponding to the frequency in (a)(iii) using section 1 of the data booklet.

[1]
a.iv.

Deduce any change in the colour of the electrolyte during electrolysis.

[1]
c.iv.

Deduce the gas formed at the anode (positive electrode) when graphite is used in place of copper.

[1]
c.v.

Explain why transition metals exhibit variable oxidation states in contrast to alkali metals.

 

[2]
d.

Markscheme

IE «= ΔE = hν = 6.63 × 10–34 J s × 3.28 × 1015 s–1» = 2.17 × 10–18 «J»

[1 mark]

a.iii.

« λ = C v = 3.00 × 10 8  m s 1 3.28 × 10 15   s 1 = » 9.15 × 10–8 «m»

[1 mark]

a.iv.

no change «in colour»

 

Do not accept “solution around cathode will become paler and solution around the anode will become darker”.

[1 mark]

c.iv.

oxygen/O2

 

Accept “carbon dioxide/CO2”.

[1 mark]

c.v.

Transition metals:

«contain» d and s orbitals «which are close in energy»

OR

«successive» ionization energies increase gradually

 

Alkali metals:

second electron removed from «much» lower energy level

OR

removal of second electron requires large increase in ionization energy

[2 marks]

d.

Examiners report

[N/A]
a.iii.
[N/A]
a.iv.
[N/A]
c.iv.
[N/A]
c.v.
[N/A]
d.

Syllabus sections

Additional higher level (AHL) » Topic 19: Redox processes » 19.1 Electrochemical cells
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Additional higher level (AHL) » Topic 19: Redox processes
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