CHEMISTRY CH13 Chemical Bonding — Science STD 9 — Question

(a) A chemical reaction which involves addition of oxygen or removal of hydrogen or loss of electrons is called oxidation. \[ \begin{array}{ll} 2 Mg + O _2 \rightarrow 2 MgO & \text { (addition of oxygen) } \\ CaH _2 \rightarrow Ca + H _2 & \text { (removal of hydrogen) } \\ Fe ^{2+} \rightarrow Fe ^{3+}+ e ^{-} \text { } & \text { (loss of electron) } \end{array} \] (b) A chemical reaction which involves addition of hydrogen or removal of oxygen or gain of electrons is called reduction. \[ \begin{array}{ll} 2 Na + H _2 \rightarrow 2 NaH & \text { (addition of hydrogen) } \\ CuO + H _2 \rightarrow Cu + H _2 O & \text { (removal of oxygen) } \\ Fe ^{3+}+ e ^{-} \rightarrow Fe ^{2+} \text { } & \text { (gain of electron) } \end{array} \]