Identify the substances that are oxidised and the substances that are reduced in the following reactions
i. \[4Na_{(s)}+O_{2(g)} \rightarrow 2Na_2O_{(s)}\]
ii. \[CuO_{(s)}+H_{2(g)} \rightarrow Cu_{(s)}+H_2O_{(l)}\]
Answers (1)
i. Any species is said to be oxidised when it loses electrons and increases the oxidation state, while any species is said to be reduced when it gains electrons and decreases the oxidation state. Sodium (Na) is oxidised and oxygen gets reduced.
\[4Na+O_2 \rightarrow 2Na_2O\]
ii. Any species is said to be oxidised when it loses electrons and increases the oxidation state, while any species is said to be reduced when it gains electrons and decreases the oxidation state. Copper oxide (CuO) is reduced to copper (Cu) as it loses oxygen and hydrogen \(H_2\) is oxidized to water \(H_2O\)
\[
CuO + H_2 \mathrel{\mathop{\longrightarrow}^{\Delta}} Cu + H_2O
\]