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CAIE IGCSE Chemistry 7.3.3 Hydrated Substance As a Substance That Questions

Work through real CAIE IGCSE Chemistry questions to identify hydrated salts and obtain anhydrous products by controlled heating.

Syllabus
2026–2028
Course
Chemistry 0620

Exam points

  • define hydrated crystals as crystals containing water of crystallisation
  • distinguish hydrated and anhydrous salts after heating
  • write the formula of an anhydrous salt formed from a hydrated salt
  • describe heating and checking that all water of crystallisation has been removed

CAIE IGCSE Chemistry 7.3.3 Hydrated Substance As a Substance That Questions question 1

[Maximum number: 1]

This question is about sulfuric acid and salts that are made from sulfuric acid.

Nickel(II) sulfate crystals contain water of crystallisation.

When nickel(II) sulfate crystals, NiSO4⋅×H2O\mathrm{NiSO}_{4} \cdot \times \mathrm{H}_{2} \mathrm{O}, are heated, they give off water.

NiSO4⋅xH2O( s)→NiSO4( s)+xH2O( g)\mathrm{NiSO}_{4} \cdot \mathrm{xH}_{2} \mathrm{O}(\mathrm{~s}) \rightarrow \mathrm{NiSO}_{4}(\mathrm{~s})+\mathrm{xH}_{2} \mathrm{O}(\mathrm{~g})

A student carries out an experiment to determine the value of x in NiSO4⋅xH2O\mathrm{NiSO}_{4} \cdot \mathbf{x} \mathrm{H}_{2} \mathrm{O}.
step 1 Nickel(II) sulfate crystals are weighed.
step 2 Nickel(II) sulfate crystals are heated.
step 3 The remaining solid is allowed to cool and is then weighed.
step 4 The remaining solid is heated again, allowed to cool and is then weighed.
step 5 Step 4 is repeated until there is no change in mass.

State the term used to describe crystals that contain water of crystallisation.

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