State what is meant by the term – chemical formula. Give the chemical formula of –

(a) sodium hydroxide

(b) sodium nitrate

(c) sodium bicarbonate

(d) sodium sulphite

(e) magnesium nitrate

(f) ammonium sulphate

(g) carbonic acid

(h) calcium phosphate

Chemical formula is the representation of a substance by means of symbols. It denotes in a compound, the number of atoms of each element present.

(a) Sodium hydroxide

$\text{Na}^{1+} \phantom{\nearrow} \text{OH}^{1-} \\[0.5em] \overset{\phantom{1}{1}}{\text{Na}} \space {\searrow}\mathllap{\swarrow} \space \overset{1}{\text{OH}} \Rightarrow \underset{\phantom{}1{}}{\text{Na}} \space {\searrow}\mathllap{\swarrow} \space \underset{1}{\text{OH}} \\[0.5em]$

So, we get the formula as $\bold{Na}\bold{OH}$

(b) Sodium nitrate

$\text{Na}^{1+} \phantom{\nearrow} \text{NO}$3^{1-} \\[0.5em] \overset{\phantom{1}{1}}{\text{Na}} \space {\searrow}\mathllap{\swarrow} \space \overset{1}{\text{NO}3} \Rightarrow \underset{\phantom{}1{}}{\text{Na}} \space {\searrow}\mathllap{\swarrow} \space \underset{1}{\text{NO}_3} \\[0.5em]

So, we get the formula as $\bold{Na}\bold{NO}_3$

(c) Sodium bicarbonate

$\text{Na}^{1+} \phantom{\nearrow} \text{HCO}$3^{1-} \\[0.5em] \overset{\phantom{1}{1}}{\text{Na}} \space {\searrow}\mathllap{\swarrow} \space \overset{1}{\text{HCO}3} \Rightarrow \underset{\phantom{}1{}}{\text{Na}} \space {\searrow}\mathllap{\swarrow} \space \underset{1}{\text{HCO}_3} \\[0.5em]

So, we get the formula as $\bold{Na}\bold{HCO}_3$

(d) Sodium sulphite

$\text{Na}^{1+} \phantom{\nearrow} \text{SO}$3^{2-} \\[0.5em] \overset{\phantom{1}{1}}{\text{Na}} \space {\searrow}\mathllap{\swarrow} \space \overset{2}{\text{SO}3} \Rightarrow \underset{\phantom{}2{}}{\text{Na}} \space {\searrow}\mathllap{\swarrow} \space \underset{1}{\text{SO}_3} \\[0.5em]

So, we get the formula as $\bold{Na}$2\bold{SO}3

(e) Magnesium nitrate

$\text{Mg}^{2+} \phantom{\nearrow} \text{NO}$3^{1-} \\[0.5em] \overset{\phantom{1}{2}}{\text{Mg}} \space {\searrow}\mathllap{\swarrow} \space \overset{1}{\text{NO}3} \Rightarrow \underset{\phantom{2}{1}}{\text{Mg}} \space {\searrow}\mathllap{\swarrow} \space \underset{2}{\text{NO}_3} \\[0.5em]

So, we get the formula as $\bold{Mg}\bold{(NO}$3)2

(f) Ammonium sulphate

$\text{NH}$4^{1+} \phantom{\nearrow} \text{SO}4^{2-} \\[0.5em] \overset{\phantom{1}{1}}{\text{NH}4} \space {\searrow}\mathllap{\swarrow} \space \overset{2}{\text{SO}4} \Rightarrow \underset{\phantom{2}{2}}{\text{NH}4} \space {\searrow}\mathllap{\swarrow} \space \underset{1}{\text{SO}4} \\[0.5em]

So, we get the formula as $\bold{(NH}$4)2\bold{SO}_4

(g) Carbonic acid

$\text{H}^{1+} \phantom{\nearrow} \text{CO}$3^{2-} \\[0.5em] \overset{\phantom{1}{1}}{\text{H}} \space {\searrow}\mathllap{\swarrow} \space \overset{2}{\text{CO}3} \Rightarrow \underset{\phantom{2}{2}}{\text{H}} \space {\searrow}\mathllap{\swarrow} \space \underset{1}{\text{CO}3} \\[0.5em] So, we get the formula as $\bold{H}2\bold{CO}_3$

(h) Calcium phosphate

$\text{Ca}^{2+} \phantom{\nearrow} \text{PO}$4^{3-} \\[0.5em] \overset{\phantom{1}{2}}{\text{Ca}} \space {\searrow}\mathllap{\swarrow} \space \overset{3}{\text{PO}4} \Rightarrow \underset{\phantom{2}{3}}{\text{Ca}} \space {\searrow}\mathllap{\swarrow} \space \underset{2}{\text{PO}_4} \\[0.5em]

So, we get the formula as $\bold{Ca}$\bold{3}\bold{(PO4)_2}