Reacting acids with bases
3 marks · NormalGroup 1 metal oxides behave differently from most other metal oxides when mixed with water.
Explain, using examples, which metal oxides form alkalis when dissolved in water.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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Must show: Reference to Group 1/alkali metals, Explanation of reaction with water, Example equations (e.g. Na2O + H2O → 2NaOH)
Common mistakes: Thinking all metal oxides are soluble; Naming insoluble Group 2 oxides as alkalis
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Marking points
M1 · 1 mark · Identifies that Group 1 metal oxides form soluble alkalis.
M2 · 1 mark · Explains that these oxides dissolve in water to form metal hydroxides (alkali).
A1 · 1 mark · Provides valid example(s) with correct equations (e.g. Na2O + H2O → 2NaOH).
Worked solution
Group 1 metal oxides (such as sodium oxide and potassium oxide) form alkalis when they dissolve in water.
They react with water to form soluble metal hydroxides, which are alkalis. For example:
Most other metal oxides (such as copper(II) oxide) are not soluble and do not form alkalis.