Question

Which has highest pH:-

• A. $CH_3COOK$
• B. $Na_2CO_3$
• C. $NH_4Cl$
• D. $NaNO_3$

Answer 1

Answer: (B)

$Na_2CO_3$

Answer 2

$pH = log \frac{1}{[H^+]}$
pH is inversely proportional to hydrogen ion concentration. As concentration of $H^+$ + decreases pH increases and vice-versa.
Ammonium chloride $(NH_4Cl)$ is a salt of weak base and strong acid. So, its aqueous solution will be acidic as
$\, \, \, \, NH_4Cl + H_2O \rightarrow _{Weak\, \, Base}^{NH_4OH} + _{Strong\, \, Acid}^{HCl}$
So, pH of $NH_4Cl$ is less than 7
Sodium nitrate $(NaNO_3)$ is the salt of strong acid and strong base. So, its aqueous solution is neutral as
$NaNO_3 + H_2O \rightarrow _{Strong\, \, Base}^{NaOH} + _{Strong\, \, acid}^{HNO_3}$
So, pH of $NaNO_3$ is 7
Potassium acetate $(CH_3COOK)$ is a salt of strong base and weak acid. Its aqueous solution will be basic and its pH value will be $> 7 \approx 8.8$
$CH_3COOK + H_2O \rightarrow _{Weak\, \, Acid}^{CH_3COOH} + _{Strong\, \, base}^{KOH}$
Sodium carbonate $(Na_2CO_3)$ is a salt of strong base and weak acid. Its aqueous solution is also basic and its pH value will be more than 10, i.e. highest among them.
$Na_2CO_3 + H_2O \rightarrow _{Strong\, \, base}^{2NaOH} + _{Weak\, \, acid}^{H_2CO_3}$