Following solutions were prepared by mixing different volumes of NaOH and HCl of different concentrations :

A. 60 mL $${M \over {10}}$$ HCl + 40 mL $${M \over {10}}$$ NaOH

B. 55 mL $${M \over {10}}$$ HCl + 45 mL $${M \over {10}}$$ NaOH

C. 75 mL $${M \over {5}}$$ HCl + 25 mL $${M \over {5}}$$ NaOH

D. 100 mL $${M \over {10}}$$ HCl + 100 mL $${M \over {10}}$$ NaOH

pH of which one of them will be equal to 1?

Concentration of the Ag⁺ ions in a saturated solution of Ag₂C₂O₄ is 2.2 $$ \times $$ 10^$$-$$4 mol L^$$-$$1. Solubility product of Ag₂C₂O₄ is

The percentage of pyridine (C₅H₅N) that forms pyridinium ion (C₅H₅N⁺H) ina 0.10 M aqueous pyridine solution (K_b for C₅H₅N = 1.7 $$ \times $$ 10^$$-$$9) is

Which of the following fluro-compounds is most likely to behave as a Lewis base ?