Which of the following titrations will have the highest pH at the equivalence po

Question

Which of the following titrations will have the highest pH at the equivalence point (assuming identical initial concentrations of all reactants)? a) Titration of C_6H_2NH_2 (a weak base) with HCI b) Titration of C_2H_5NH_2 (a weak base) with HCI c) Titration of HCIO_4 with NaOH d) Titration of HBrO with NaOH c) Titration of HIO acid with NaOH 2. A 30.00 mL sample of a 0.100 M aqueous solution of a weak acid HA is titrated with a 0.200 M aqueous solution of NaOH. At which point in the titration will the [H_3O^+] be equal to K_a of the weak acid? a) after addition of 7.50 mL of the NaOH solution b) after addition of 15.00 mL of the NaOH solution c) after addition of 22.50 mL of the NaOH solution d) after addition of 30.00 mL of the NaOH 3. Which of the following systems is the best system for preparing a buffered solution having a pH = 5.00? a) benzoic acid/benzoate b) formic acid/formate c) nitrous acid/nitrite d) propionic acid/propionate 4. In an experiment, a 50.00 mL sample of a 0.3250 M aqueous solution of a weak acid, HA, is titrated with an aqueous solution of NaOH. The net ionic equation for the titration is show below: HA + OH^- rightarrow A^- + H_2O At which point(s) in the titration will the resulting solution will be buffered after the reaction between HA and OH^- is complete? i) After addition of 0.006522 mol of OH^- ii) after addition of 0.01625 mol of OH^- iii) after addition of 0.02258 mol of OH^- a) i only b) ii only c) iii only d) i an ii c) ii and iii

Explanation / Answer

Solution :-

Q1) when the weak acid and strong base are titrated then at the equivalence point the conjugate base of weak acid dissociates and forms the basic solution at the equivalence point

So the answer is option d and e because the HBrO and HIO are weak acids which are reacted with strong base NaOH

Q2) HA is monoprotic acid and NaOH is also monobasic so they react in 1 :1 ratio

So when the 30 ml of 0.100 M acid is used then to reach the half equivalence point 7.5 ml of 0.200 M NaOH is required so at that point the [H3O+] is same as ka so the answer is option A

Q3) benzoic acid has the ka which is 6.3*10^-6

So it is good to have the buffer with pH 5.00

So the answer is benzoic acid /benzoate that is option A

Q4) lets first find the moles of HA

Moles of HA= molarity * volume in liter

                       = 0.3250 mol per L * 0.050 L

                      = 0.01625 mol HA

To make the buffer solution we need moles of OH- less than moles of HA

So the answer is option A where moles of OH- are less than moles of HA

So the answer is option A that is I only

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