Differences between the properties of metals and non-metals
4 marks · NormalState what is meant by a basic oxide and give one example of a basic oxide formed by a metal.
Explain, using a chemical equation, how an acidic oxide formed by a non-metal reacts with an alkali.
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(a) A basic oxide reacts with acids to form salts. Example: copper(II) oxide (CuO) is a basic oxide.
(b) Carbon dioxide (CO2) is an acidic oxide. It reacts with sodium hydroxide (NaOH, an alkali) as follows: CO2 + 2NaOH → Na2CO3 + H2O.
Also accept: Basic oxide forms salts with acids; copper(II) oxide, magnesium oxide, etc.; CO2 (acidic oxide) + NaOH (alkali) → Na2CO3 + H2O
Common mistakes: Confusing acidic and basic oxides; Omitting water in the chemical equation
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Marking points
B1 (a) · 1 mark · Correctly defines basic oxide.
B2 (a) · 1 mark · Gives correct example of a basic oxide (e.g., CuO, MgO, Na2O).
M1 (b) · 1 mark · States correct acidic oxide reaction with alkali in words or chemical symbols.
A1 (b) · 1 mark · Gives balanced chemical equation for acidic oxide and alkali reaction (e.g., CO2 + 2NaOH → Na2CO3 + H2O).
Worked solution
a) A basic oxide is an oxide that reacts with acids to form a salt. An example of a basic oxide is copper(II) oxide (CuO). b) An acidic oxide, such as carbon dioxide (CO2), reacts with alkalis to form salts and water. The balanced equation is: