Date | November 2009 | Marks available | 2 | Reference code | 09N.2.hl.TZ0.3 |
Level | HL | Paper | 2 | Time zone | TZ0 |
Command term | Determine | Question number | 3 | Adapted from | N/A |
Question
Describe the emission spectrum of hydrogen. Outline how this spectrum is related to the energy levels in the hydrogen atom.
Transition elements form complexes such as [Fe(CN)6]4− and [FeCl4]−. Deduce the oxidation number of iron in each of these complex ions.
[Fe(CN)6]4−
[FeCl4]−
Markscheme
series of lines/lines;
electron transfer/transition between higher energy level to lower energy level / electron transitions into first energy level causes UV series / transition into second energy level causes visible series / transition into third energy level causes infrared series;
convergence at higher frequency/energy/short wavelength;
Allow any of the above points to be shown on a diagram.
[Fe(CN)6]4−=+2;
[FeCl4]−=+3;
Award [1 max] if 2+ and 3+, 2 and 3 or II and III stated.
Examiners report
In the emission spectrum of hydrogen some candidates missed stating about convergence at high energy/frequency while some other candidates forgot to write that it is a line spectrum.
The majority of candidates deduced the oxidation number of iron in the complex ions correctly although some candidates still wrote 2+ and 3+ which deprived them of one mark.