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Reviewed CSCA Chemistry question · Standard

A 0.150 mol sample of hydrated copper(II) sulfate, CuSO4·5H2O, is heated until all water of crystallization is removed. How many moles of water molecules are released?

  1. 0.150 mol
  2. 0.750 mol
  3. 1.50 mol
  4. 0.0300 mol
Show the answer and explanation

Correct answer

B. 0.750 mol

Principle or equation

The formula CuSO4·5H2O indicates that each formula unit contains 5 water molecules. Therefore, the amount of water is 5 times the amount of the hydrate.

Why this answer is correct

Multiply the amount of hydrate by the number of water molecules per formula unit: 0.150 mol × 5 = 0.750 mol.

Example

For 0.200 mol of Na2CO3·10H2O, water released = 0.200 × 10 = 2.00 mol.

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