A student tries to make a pure, dry sample of hydrated copper(II) sulfate crystals. She uses dilute sulfuric acid and solid copper(II) oxide. This is the student's method:
Her sample of copper(II) oxide contains a small amount of solid impurity that dissolves in water, but does not react with the acid.
State why it is not necessary to have a precise measurement of the volume of sulfuric acid in step 1.
State why the acid is warmed in step 2.
Suggest why a glass rod, rather than a metal spatula, is used to stir the mixture in step 3.
State how the student will know when the copper(II) oxide stops reacting in step 4.
State why the method used in step 6 will not produce a pure sample of hydrated copper(II) sulfate crystals.
Describe how the student could produce a pure, dry sample of crystals from the filtrate in step 5.
The table below shows the formula and colour of three different types of copper(II) sulfate.
| Formula | Colour |
|---|---|
| CuSO4\text{CuSO}_4CuSO4 | white |
| CuSO4⋅H2O\text{CuSO}_4\cdot\text{H}_2\text{O}CuSO4⋅H2O | pale blue |
| CuSO4⋅5H2O\text{CuSO}_4\cdot5\text{H}_2\text{O}CuSO4⋅5H2O | blue |
When water is added very slowly to solid CuSO4\text{CuSO}_4CuSO4, the colour changes from white to pale blue and then to blue.
Write a chemical equation for the change from the pale blue solid to the blue solid.
Which of these words describes the change taking place when the blue solid is heated to form the white solid?
