Q6 / 75 · JEE Main 2026 (05 April Shift 1) · Chemistry

Arrange the following resultant mixtures in increasing order of their pH values
A. $10$ mL $0.2$ M Ca(OH)$_2$ + $25$ mL $0.1$ M HCl
B. $10$ mL $0.01$ M H$_2$SO$_4$ + $10$ mL $0.01$ M Ca(OH)$_2$
C. $10$ mL $0.1$ M H$_2$SO$_4$ + $10$ mL $0.1$ M KOH
Choose the correct answer from the options given below:

  • A
    $B < C < A$
  • B
    $C < A < B$
  • Correct answer
    C
    $C < B < A$
  • D
    $A < C < B$

Solution

For mixture A:
Millimoles of OH$^{-}$ = $10 \times 0.2 \times 2 = 4$
Millimoles of H$^{+}$ = $25 \times 0.1 \times 1 = 2.5$
Remaining OH$^{-}$ = $4 - 2.5 = 1.5$ mmol
The solution is basic, so pH $> 7$.

For mixture B:
Millimoles of H$^{+}$ = $10 \times 0.01 \times 2 = 0.2$
Millimoles of OH$^{-}$ = $10 \times 0.01 \times 2 = 0.2$
The solution is completely neutralized, so pH $= 7$.

For mixture C:
Millimoles of H$^{+}$ = $10 \times 0.1 \times 2 = 2$
Millimoles of OH$^{-}$ = $10 \times 0.1 \times 1 = 1$
Remaining H$^{+}$ = $2 - 1 = 1$ mmol
The solution is acidic, so pH $< 7$.

Therefore, the increasing order of pH values is C $<$ B $<$ A.

Answer: $C < B < A$

Hence, the correct answer is option: 'C'.

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