CIE iGCSE Co-Ordinated Science C10.1 Water Exam Style Questions Paper 1
▶️ Answer/Explanation
When added to water, anhydrous copper(II) sulfate dissolves to form a blue solution. Anhydrous cobalt(II) chloride dissolves to form a pink solution. Both compounds change colour when hydrated (copper(II) sulfate turns blue, cobalt(II) chloride turns pink). Therefore, row B correctly shows these colours.
✅ Answer: (B)
✅ Answer: (B)
▶️ Answer/Explanation
Pure water is neutral, so universal indicator turns green (pH 7). Anhydrous copper(II) sulfate is a white powder that turns blue in the presence of water. Therefore, pure water gives a green colour with universal indicator and turns anhydrous copper(II) sulfate blue.
✅ Answer: (C)
✅ Answer: (C)
▶️ Answer/Explanation
When water is added to white anhydrous copper(II) sulfate, it turns blue (forming hydrated copper(II) sulfate, \(\text{CuSO}_4 \cdot 5\text{H}_2\text{O}\)).
When water is added to blue anhydrous cobalt(II) chloride, it turns pink (forming hydrated cobalt(II) chloride); this matches option C.
✅ Answer: (C)
When water is added to blue anhydrous cobalt(II) chloride, it turns pink (forming hydrated cobalt(II) chloride); this matches option C.
✅ Answer: (C)
▶️ Answer/Explanation
The three key fertiliser elements are nitrogen, phosphorus and potassium (NPK).
Potassium nitrate, \(KNO_3\), contains both potassium and nitrogen.
The other compounds (carbonate, chloride, sulfate) only supply potassium plus a non-fertiliser element.
✅ Answer: (C)
Potassium nitrate, \(KNO_3\), contains both potassium and nitrogen.
The other compounds (carbonate, chloride, sulfate) only supply potassium plus a non-fertiliser element.
✅ Answer: (C)
▶️ Answer/Explanation
Anhydrous cobalt(II) chloride is blue when dry but turns pink when water is added.
This colour change is a reliable chemical test that specifically confirms the presence of water, unlike a physical test such as measuring the boiling point.
✅ Answer: (A)
This colour change is a reliable chemical test that specifically confirms the presence of water, unlike a physical test such as measuring the boiling point.
✅ Answer: (A)