CAIE IGCSE Chemistry 7.2.1 Classify oxides as acidic

Practise deciding whether oxides are acidic or basic from their elements, pH in water, indicator changes and reactions with bases.

Exam points

classify SO2 or CO2 as acidic oxides and CuO or CaO as basic oxides
interpret pH or indicator results after oxides dissolve in water
link non-metal oxides with acidic behaviour and metal oxides with basic behaviour

[Maximum number: 2]

Iron ore contains iron(III) oxide, $\mathrm{Fe}_{2} \mathrm{O}_{3}$ . A blast furnace is used to extract iron from $\mathrm{Fe}_{2} \mathrm{O}_{3}$ .
Equations for some of the reactions in the blast furnace are shown.

$equation $1 \mathrm{C}+\mathrm{O}_{2} \rightarrow \mathrm{CO}_{2}$$

$equation $2 \mathrm{CaCO}_{3} \rightarrow \mathrm{CaO}+\mathrm{CO}_{2}$$

$equation $3 \quad \mathrm{CaO}+\mathrm{SiO}_{2} \rightarrow \mathrm{CaSiO}_{3}$$

Explain why the reaction in equation 3 can be described as an acid-base reaction.

M1 CaO is basic

M2 $\mathrm{SiO}_{2}$ is acidic

All question bank results loaded

7.2.1—Classify oxides as acidic question 1