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Chemistry · Oct / Nov 2021 · Paper 62 · Question 4

0620

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Cobalt is a metal. Cobalt is between copper and iron in the reactivity series. The mineral spherocobaltite contains the compound cobalt(II) carbonate and no other metal ions. Cobalt(II) carbonate is insoluble in water and reacts with dilute acids to form an aqueous solution of a salt. Describe how you would obtain a sample of cobalt metal starting with a large lump of spherocobaltite. You have access to all normal laboratory apparatus and chemicals. [6]

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reduction method

Any 6 from:

crush rock / break into smaller pieces / powder
using a suitable method, e.g. pestle and/or mortar, hammer
add more reactive metal / suitable gas
carbon / coke / zinc / aluminium / magnesium / CO / hydrogen specified
heat
In a suitable container (e.g. crucible, evaporating basin)
cobalt displaced / cobalt formed

electrolysis method

Any 6 from:

crush rock / break into smaller pieces / powder
using a suitable method, e.g. pestle and / or mortar, hammer
add a (dilute) acid
suitable strong acid named (e.g. HCl, H2SO4, HNO3)
electrolysis (of solution)
specified inert material for electrodes (e.g. carbon, platinum)
cobalt obtained at the negative electrode / cathode

displacement method

Any 6 from:

crush rock / break into smaller pieces / powder
using a suitable method, e.g. pestle and / or mortar, hammer
add a (dilute) acid
suitable strong acid named (e.g. HCl, H2SO4, HNO3)
add metal more reactive than cobalt
name of metal added specified (e.g. iron, zinc, magnesium)
Cobalt displaced / cobalt formed
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