Arrange the following resultant mixtures in increasing order of their pH values

A. $10 \mathrm{~mL} 0.2 \mathrm{M} \mathrm{Ca}(\mathrm{OH})_2+25 \mathrm{~mL} 0.1 \mathrm{M} \mathrm{HCl}$

B. $10 \mathrm{~mL} 0.01 \mathrm{M} \mathrm{H}_2 \mathrm{SO}_4+10 \mathrm{~mL} 0.01 \mathrm{M} \mathrm{Ca}(\mathrm{OH})_2$

C. $10 \mathrm{~mL} 0.1 \mathrm{M} \mathrm{H}_2 \mathrm{SO}_4+10 \mathrm{~mL} 0.1 \mathrm{M} \mathrm{KOH}$

Choose the correct answer from the options given below :

Given below are two statements :

Statement I : Sodium dichromate and potassium dichromate are classified as primary standards in titrimetric analysis.

Statement II : Phenolphthalein is a weak base, therefore it dissociates in acidic medium.

In the light of the above statements, choose the correct answer from the options given below

20 mL of a solution of acetic acid required 28.4 mL of 0.1 M NaOH for its neutralization. A solution (X) was prepared by mixing 20 mL of the above acetic acid and 14.2 mL of 0.1 M NaOH solution. What is the pH of the solution $(\mathrm{X})$ ? $\left(\mathrm{pK}_{\mathrm{a}}\right.$ value of acetic acid is 4.75).

The first and second ionization constants of a weak dibasic acid H₂A are $8.1 \times 10^{-8}$ and $1.0 \times 10^{-13}$ respectively. 0.1 mol of H₂A was dissolved in 1 L of 0.1 M HCl solution. The concentration of HA^- in the resultant solution is: