1.4) Chemical Changes - EXAM QUESTIONS Flashcards
A student added copper oxide to sulfuric acid. The reaction made copper sulfate solution. Describe how the student could obtain dry copper sulfate crystals from the solution.
[4 marks]
Heat the solution over a water bath. [1]
Heat until crystals start to form around the edge. [1]
Leave for a few days until all the water has evaporated. [1]
Dry the crystals with filter paper/in an oven. [1]
A student adds small pieces of magnesium and copper to separate test tubes of dilute acid. Compare the observations she would make in the two test tubes.
[4 marks]
There would be rapid bubbling in the test tube with magnesium. [1]
However, there would be no bubbling in the test tube with copper. [1]
The magnesium would be smaller/disappear by the end of the reaction. [1]
However, the copper would be unchanged. [1]
Sulfuric acid is a strong acid. What is meant by a strong acid?
[2 marks]
The acid is fully ionised/all the molecules are dissociated. [1]
This happens in aqueous solution/when dissolved in water. [1]
Aluminium is extracted from aluminium oxide by electrolysis.
In the electrolysis cell, there is a mixture of aluminium oxide and molten cryolite. Explain why.
[3 marks]
The mixture of aluminium oxide and molten cryolite melts at a lower temperature than aluminium oxide alone. [1]
This reduces the amount of energy required by the process. [1]
This therefore reduces costs. [1]
- (strong because) completely
onised (in aqueous solution) - (dilute because) small amount of
acid per unit volume
50
pipette measures a fixed volume
(accurately)
(but) burette measures variable
volume)
