DP Chemistry (last assessment 2024)

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Question 19M.3.hl.TZ2.6b

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Date May 2019 Marks available [Maximum mark: 3] Reference code 19M.3.hl.TZ2.6b
Level hl Paper 3 Time zone TZ2
Command term Determine Question number b Adapted from N/A
b.
[Maximum mark: 3]
19M.3.hl.TZ2.6b

Calcium has a face-centred cubic (cubic close packing) arrangement of atoms.

(b)

Determine the density of calcium, in g cm−3, using section 2 of the data booklet.

Ar = 40.08; metallic radius (r) = 1.97 × 10−10 m

[3]

Markscheme

a = «  4 r 2 = 4 × 1.97 × 10 − 10 m 2 =» 5.572 × 10–10 «m»
OR
volume of unit cell = «(5.572 × 10–10 m)3 × 106 =» 1.73 × 10–22 «cm3»  [✔]

mass of unit cell =«  40.08  g mo l − 1 × 4 6.02 × 10 23 mo l − 1 =» 2.66 × 10–22 «g»  [✔]

density = «  2.66 × 10 − 22 g ( 5.572 × 10 − 10 ) 3 × 10 6 » 1.54 «g cm–3»  [✔]

 

Note: Award [3] for correct final answer.

Examiners report

Majority of the candidates managed to get three marks in determining the density of the calcium.

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