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JEE Main 202315 AprilMorning Shift
Exam
JEE Main
Year
2023
Date
15 April
Shift
Morning Shift
Subject
Chemistry
Chapter
Ionic Equilibrium

JEE Main 2023 · 15 April · Morning Shift · Chemistry · Ionic Equilibrium

Which of the following statement(s) is/are correct? (A) The pH of 1...

Which of the following statement(s) is/are correct?

(A) The pHpH of 1×10–8MHCl1 \times {10}^{– 8}MHCl solution is 88.

(B) The conjugate base of H2PO4−{H}_{2}{PO}^{4 -} is HPO42−{HPO}_{4}^{2 -}.

(C) Kw{K}_{w} increases with increase in temperature.

(D) When a solution of a weak monoprotic acid is titrated against a strong base at half neutralisation point, pH=12pKapH = \dfrac{1}{2}{pK}_{a}. Choose the correct answer from the options given below:

Options

  1. A(B),(C)\left(B\right), \left(C\right)
  2. B(A),(D)\left(A\right), \left(D\right)
  3. C(A),(B),(C)\left(A\right), \left(B\right), \left(C\right)
  4. D(B),(C),(D)\left(B\right), \left(C\right), \left(D\right)

Correct answer

A. (B),(C)\left(B\right), \left(C\right)

Step-by-step solution

When concentration of H+{H}^{+} ion is more than 10−7M{10}^{- 7}M, the proton concentration from water must be considered. Hence, the pH of 10−8MHCl{10}^{- 8}MHCl solution is not equal to 8.

H2PO4−Acid⇌HPO42−Conjugatebase+H+\mathop{{H}_{2}{PO}_{4}^{-}}_{Acid}\overset{}{⇌}\mathop{{HPO}_{4}^{2 -}}_{Conjugatebase} + {H}^{+}

Kw{K}_{w} increase with increase in temperature as dissociation of water increases with increase in temperature.

When weak monoprotic acid is titrated against strong base, at half neutralization point, the solution becomes acidic buffer and its pHpH is given by

pH=pKa+log[Salt][Acid]pH = {pK}_{a} + log\dfrac{\left[Salt\right]}{\left[Acid\right]}

⇒pH=pKa+0⇒ pH = {pK}_{a} + 0 as \left[salt\right] = \left[acid\right]$

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