What are Diprotic and Triprotic acid ? differentiation eat .

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Polyprotic acid : The acids which have more than one ionizable proton per molecule of the acid. Such acids are known as polybasic or polyprotic acids.

Diprotic acid : The acid which have two ionizable proton per molecule of the acid. Such acids are known as Dibasic or Diprotic acid.

e.g., $\mathrm{H}_{2} \mathrm{X}+{ }_{\text {(aq) }}+2 \mathrm{H}^{+}+\mathrm{X}^{2-} \quad \mathrm{K}_{a}$

The ionization of the reaction is in two steps is as under,

$(i)$ $\mathrm{H}_{2} \mathrm{X}+\mathrm{H}_{2} \mathrm{O}+\mathrm{H}_{3} \mathrm{O}^{+}+\mathrm{HX}^{-} \quad \mathrm{K}_{a}$ (i)

$(ii)$ $\mathrm{HX}^{-}+\mathrm{H}_{2} \mathrm{O}+\mathrm{H}_{3} \mathrm{O}^{+}+\mathrm{X}^{2-} \quad \mathrm{K}_{a}$ (ii)

In it, $\mathrm{K}_{a}$ (i) $>\mathrm{K}_{a}$ (ii) and $\mathrm{K}_{a}$ (i) $\times \mathrm{K}_{a}$ (ii) $=\mathrm{K}_{a}$

Examples of diprotic acid : Oxalic acid $\left(\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\right)$, Sulphuric acid $\left(\mathrm{H}_{2} \mathrm{SO}_{4}\right)$, Carbonic acid

$\left(\mathrm{H}_{2} \mathrm{CO}_{3}\right)$, Sulphurous acid $\left(\mathrm{H}_{2} \mathrm{SO}_{3}\right)$, Ascorbic acid etc.

Examples of triprotic acid : Phosphoric acid $\left(\mathrm{H}_{3} \mathrm{PO}_{4}\right)$, Cytaric acid.... etc.

In polyprotic acid solution constant mixture of acid like $\mathrm{H}_{2} \mathrm{~A}, \mathrm{HA}^{-}$and $\mathrm{A}^{2-}$.

Similar Questions

The $pH$ of two equimolar weak acids are $3.0$ and $5.0$ respectively. Their relative strength is

When $100 \ mL$ of $1.0 \ M \ HCl$ was mixed with $100 \ mL$ of $1.0 \ M \ NaOH$ in an insulated beaker at constant pressure, a temperature increase of $5.7^{\circ} C$ was measured for the beaker and its contents (Expt. $1$). Because the enthalpy of neutralization of a strong acid with a strong base is a constant $\left(-57.0 \ kJ \ mol ^{-1}\right)$, this experiment could be used to measure the calorimeter constant. In a second experiment (Expt. $2$), $100 \ mL$ of $2.0 \ M$ acetic acid $\left(K_a=2.0 \times 10^{-5}\right)$ was mixed with $100 \ mL$ of $1.0 M \ NaOH$ (under identical conditions to Expt. $1$) where a temperature rise of $5.6^{\circ} C$ was measured.

(Consider heat capacity of all solutions as $4.2 J g ^{-1} K ^{-1}$ and density of all solutions as $1.0 \ g mL ^{-1}$ )

$1.$ Enthalpy of dissociation (in $kJ mol ^{-1}$ ) of acetic acid obtained from the Expt. $2$ is

$(A)$ $1.0$ $(B)$ $10.0$ $(C)$ $24.5$ $(D)$ $51.4$

$2.$ The $pH$ of the solution after Expt. $2$ is

$(A)$ $2.8$ $(B)$ $4.7$ $(C)$ $5.0$ $(D)$ $7.0$

Give the answer question $1$ and $2.$

  • [IIT 2015]

$25$ $mL$ $0.1$ $M$ $HCl$ solution is diluted till $500$ $mL$. Calculate $pH$ of dilute solution.

The degree of ionization of a $0.1 \,M$ bromoacetic acid solution is $0.132$ Calculate the $pH$ of the solution and the $p K_{ a }$ of bromoacetic acid.

What is the $pH$  of $0.1\,M\,N{H_3}$