Question 1

During the titration of a weak base (such as NH$$_3) $$with a strong acid (such as HCl), what is the pH at the half-equivalence point?

Accepted Answer

pH = 14 - pK_b

Question 2

Which equation is used to calculate the pH of a buffer solution formed during the titration of a weak base with a strong acid, before the equivalence point?

Accepted Answer

$$\mathrm{pOH} = \mathrm{p}K_b + \log \left( \frac{[\mathrm{BH}^+]}{[\mathrm{B}]} \right)$$

Question 3

A student titrates 25.00 mL of 0.500 M propanoic acid (CH$$_3CH$_2$$COOH, $$K_a = 1.3 	imes 10$$^{-5}$$) with 1.005 M NaOH. What is the main species present at the equivalence point?

Accepted Answer

CH$$_3CH$_2$$COO^-$

Question 4

Which of the following best describes the pH at the equivalence point during the titration of a weak base with a strong acid?

Accepted Answer

The pH is acidic (pH \u003c 7)

Question 5

For the titration of a polyprotic acid such as H$$_3PO$_4$$, how many equivalence points are observed and what do they represent?

Accepted Answer

Three equivalence points, each representing the loss of one proton

Question 6

Which calculation is necessary to determine the pH after the equivalence point in a titration of a weak base with a strong acid?

Accepted Answer

Calculate the excess strong acid moles and use $$\mathrm{pH} = -\log [\mathrm{H}_3\mathrm{O}^+]$$

Question 7

During the titration of a weak acid with a strong base, what is the pH at the equivalence point?

Accepted Answer

pH \u003e 7

Question 8

Which of the following is true about the buffer region in a titration curve of a weak base with a strong acid?

Accepted Answer

It occurs before the equivalence point, where both weak base and its conjugate acid are present

Question 9

A titration curve for a weak base and strong acid shows a sharp decrease in pH at the equivalence point. What causes this?

Accepted Answer

The complete conversion of the weak base to its conjugate acid

Question 10

If you titrate 0.10 M NH$$_3$$ with 0.10 M HCl, and the pH at the half-equivalence point is 9.25, what is the $$pK_b of NH$_3$$?

Accepted Answer

$$pK_b = 9.25$$

Question 11

Which of the following best explains why the pH at the equivalence point of a strong acid-strong base titration is 7.00?

Accepted Answer

The salt formed is neutral and does not hydrolyze in water

Question 12

Which formula would you use to calculate the pH at the initial point of a weak base-strong acid titration?

Accepted Answer

$$\mathrm{pOH} = -\log [\mathrm{OH}^-]$$

Question 13

In the titration of H$$_3PO$_4$$ with NaOH, what is the pH at the first midpoint?

Accepted Answer

$$\mathrm{pH} = \mathrm{p}K_{a1}$$

Question 14

Which of the following statements is correct regarding the calculation of $$K_a$$ for the conjugate acid formed at the equivalence point in a weak base-strong acid titration?

Accepted Answer

$$K_a = K_w / K_b$$

Question 15

A titration curve for a polyprotic acid shows three distinct equivalence points. What does the second equivalence point represent?

Accepted Answer

The complete removal of the second proton

Question 16

Which of the following best describes the solution at the equivalence point when titrating a weak base with a strong acid?

Accepted Answer

A solution of the weak conjugate acid

Question 17

What is the correct expression for the calculation of excess hydronium ion concentration after the equivalence point in a weak base-strong acid titration?

Accepted Answer

$$[\mathrm{H}_3\mathrm{O}^+]_{	ext{excess}} = \frac{	ext{mol H}_3\mathrm{O}^+ - 	ext{mol B}}{V_{	ext{base}} + V_{	ext{acid}}}$$

Acid-Base Titrations: Weak Bases, Polyprotic Acids, and Titration Curves

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