DP Chemistry (last assessment 2024)

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Question 17N.3.hl.TZ0.b.ii

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Date November 2017 Marks available [Maximum mark: 2] Reference code 17N.3.hl.TZ0.b.ii
Level hl Paper 3 Time zone TZ0
Command term Determine Question number b.ii Adapted from N/A
b.ii.
[Maximum mark: 2]
17N.3.hl.TZ0.b.ii

Metals have various crystal structures. Cobalt forms a face-centred cubic (FCC) lattice. Two representations of FCC are shown.

Determine a value for the density of cobalt, in g cm–3, using data from sections 2 and 6 of the data booklet and your answers from (a) and (b) (i).

If you did not obtain an answer to (b) (i), use 3.00 × 10–8 cm but this is not the correct answer.

[2]

Markscheme

mass of 4 atoms = 4 × 58.93 g m o l − 1 6.02 × 10 23 m o l − 1 = 3.916 × 10 − 22 «g»

«density  = 3.916 × 10 − 22 g ( 3.34 × 10 − 8 c m ) 3 = » 10.5 «g cm–3»

Answer using 3.00 x 10–8 cm:

mass of 4 atoms =  4 × 58.93 g m o l − 1 6.02 × 10 23 m o l − 1 = 3.916 × 10 − 22  «g»

«density  = 3.916 × 10 − 22 g ( 3.00 × 10 − 8 c m ) 3 = » 14.5 «g cm–3»

Award [2] for correct final answer.

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