Question on pH
A weak base BOH reacts with 0.1M HCl. The dissociation constant of BOH is 10–6. When 50 ml of 0.1N BOH reacts with HCl, what will the pH of the solution be at the neutralization point of the reaction?
Is a 0.01 N solution of Ca(OH)2 more basic than a 0.01 M solution of Ca(OH)2? Why?
No. 0.01 N solution of Ca(OH)2 is 0.005 M. SO, it will produce 0.01 M hydroxide ions while 0.01 M solution will produce 0.02 M hydroxide ions.
100mL of 0.05M solution of a strong acid H2A was mixed with 50mL of 0.1M solution of NH4OH. What will the pH of the resulting solution be?
pH of the resulting solution will be 3.476.
100mL of 0.1M acetic acid is mixed with 25mL of 0.1M sodium hydroxide solution. What will the pH of the resulting solution be? pKa (acetic acid) = 4.74
It can be understood from the question that 25% of the weak acid is neutralized by the strong base which will also produce a salt of the weak acid with the strong base. This will result in a acidic buffer solution.
HOAc + NaOH = NaOAc + H2O
[acid] = 75% of acid, that was originally present
[salt] = 25% of acid, that was originally present
pH = pKa + log ([salt]/[acid]) = 4.74 + log (25/75) = 4.74 – log 3 = 4.74 – 0.48 = 4.26
Why is an aqueous solution of sodium acetate alkaline?
Acetate ion gets hydrolyzed in the aqueous solution to produce hydroxide ions.
AcO- + H2O = HOAc + HO-
This increases the concentration of hydroxide ions in the solution and as a result the solution becomes alkaline.