Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
JEE Main 20254 AprilMorning Shift
Exam
JEE Main
Year
2025
Date
4 April
Shift
Morning Shift
Subject
Chemistry
Chapter
Ionic Equilibrium

JEE Main 2025 · 4 April · Morning Shift · Chemistry · Ionic Equilibrium

The pH of a 0.01 M weak acid HX(K_ a =4 × 10^ -10 ) is found to be...

The pH of a 0.01 M weak acid HX(Ka=4×10−10)\mathrm{HX}\left(\mathrm{K}_{\mathrm{a}}=4 \times 10^{-10}\right) is found to be 5. Now the acid solution is diluted with excess of water so that the pH of the solution changes to 6. The new concentration of the diluted weak acid is given as x×10−4Mx \times 10^{-4} \mathrm{M}. The value of x is ________ (nearest integer)

Correct answer

0

Step-by-step solution

HX(aq)⇌H(aq)++X(aq)−Ka=4×10−10&0.01(1−α)0.01α0.01α Not justified &⇒0.01α=10−5⇒α=10−3&Ka=0.01α2=10−8\begin{aligned}& \quad \mathrm{HX}_{(\mathrm{aq)}} \rightleftharpoons \mathrm{H}_{(\mathrm{aq})}^{+}+\mathrm{X}_{(\mathrm{aq})}^{-} \quad \mathrm{K}_{\mathrm{a}}=4 \times 10^{-10} \& 0.01(1-\alpha) \quad 0.01 \alpha \quad 0.01 \alpha \quad \text{ Not justified } \& \Rightarrow 0.01 \alpha=10^{-5} \Rightarrow \alpha=10^{-3} \& \mathrm{ K}_{\mathrm{a}}=0.01 \alpha^2=10^{-8}\end{aligned}On dilution let final concentration of HX=cM\mathrm{HX}=\mathrm{c} \mathrm{M}Hx(an)⇌H(aq)++X(an)−&C(1−α)CαCα&⇒Cα=10−6...(1)&Cα21−α=Ka=10−8...(2)&⇒10−6α1−α=10−8\begin{aligned}& \mathrm{Hx}_{(\mathrm{an})} \rightleftharpoons \mathrm{H}_{(\mathrm{aq})}^{+}+\mathrm{X}_{(\mathrm{an})}^{-} \& \mathrm{C}(1-\alpha) \quad \mathrm{C} \alpha \quad \mathrm{C} \alpha \& \Rightarrow \mathrm{C} \alpha=10^{-6}...(1) \& \quad \frac{\mathrm{C} \alpha^{2}}{1-\alpha}=\mathrm{K}_{\mathrm{a}}=10^{-8}...(2) \& \Rightarrow \frac{10^{-6} \alpha}{1-\alpha}=10^{-8}\end{aligned}$$Data given is inconsistent \& contradictory. This should be bonus.
Practice Ionic Equilibrium on Quantrex Academy →

More from Ionic Equilibrium

Given is a concentrated solution of a weak electrolyte A_xB_y of concentration 'c' and… JEE Main 2026M_3 A_2 is a sparingly soluble salt of molar mass y g mol ^ -1 and solubility x g L ^ -1… JEE Main 2026Arrange the following resultant mixtures in increasing order of their pH values A. 10 mL… JEE Main 202620 mL of a solution of acetic acid required 28.4 mL of 0.1 M NaOH for its neutralization.… JEE Main 2026The pH of a solution obtained by mixing 5 mL of 0.1 M NH_4OH solution with 250 mL of 0.1… JEE Main 2026The first and second ionization constants of a weak dibasic acid H_2 A are 8.1 × 10^ -8… JEE Main 2026At 25°C , 20.0 mL of 0.2 M weak monoprotic acid HX is titrated against 0.2 M NaOH. The pH… JEE Main 2026The solubility product constants of Ag_2CrO_4 and AgBr are 32x and 4y respectively at 298… JEE Main 2026 Full Ionic Equilibrium list All JEE Main PYQs