JAMB Chemistry 2021 Objective — Question 4

Question 4 of 41 from the Joint Admissions and Matriculation Board (JAMB) Chemistry 2021 Objective paper, with the correct answer and a full explanation.

When a few drops of water are added to a sample of anhydrous cobalt(ii) chloride, the colour of the salt becomes

A. Red
B. PinkCorrect
C. Blue
D. White

Explanation

Anhydrous CoCl₂ is blue. On hydration with water: CoCl₂ + 6H₂O → CoCl₂·6H₂O (pink). This colour change is used as a test for water.

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