Question 1

Consider the titration of 100.0 mL of the weak diprotic acid HS1U1B12S1U1B0A (0.10 M)with 0.20 M NaOH.What are the major species at each of the following points in the titration? (Water is always assumed to be a major species. )
-After 25.0 mL of 0.20 M NaOH is added

Accepted Answer

At the beginning of the titration, the weak diprotic acid H₂A is the major species in solution. As NaOH is added, it reacts with the acid to form its conjugate base and water. After 25.0 mL of 0.20 M NaOH is added, half of the total volume has been titrated (50.0 mL), which corresponds to the equivalence point for the first proton transfer reaction. At this point, half of the acid has been neutralized and converted to its conjugate base (HA^-), while the other half remains as the weak acid (H₂A). Therefore, the major species in solution are H₂A (weak acid) and its conjugate base HA^-.

Question 2

In the titration of a weak acid HA with 0.100 M NaOH,the stoichiometric point is known to occur at a pH value of approximately 11.Which of the following indicators would be best to use to mark the endpoint of this titration?

Accepted Answer

The best indicator for a titration is one whose pKa is close to the pH at the equivalence point. For a pH of 11, an indicator with a pKa of 12 (Ka = 10^-12) is closest.

Question 3

A 50.00-mL solution of 0.0304 M ethanolamine (K_b = 3.2 $\times$10^-⁵)is titrated with a 0.0282 M solution of hydrochloric acid as the titrant.What is the pH of the base solution after 23.24 mL of titrant have been added? (K_w = 1.00 $\times$10^-¹⁴)

Accepted Answer

After adding 23.24 mL of HCl, the solution is in the buffer region before the equivalence point. Use the Henderson-Hasselbalch equation to find the pH: pH = pKa + log([base]/[acid]). Calculate moles of ethanolamine and HCl, find concentrations, and use pKa = 14 - pKb to find pH.

Question 4

In the titration of a weak acid,HA,with a sodium hydroxide solution of approximately the same concentration,the stoichiometric point occurs at pH = 9.5.Which of the following weak acid indicators would be best suited to mark the endpoint of this titration?

Accepted Answer

The stoichiometric point of the titration is at pH 9.5, which is basic. The best indicator would have a pKa close to this pH. Indicator A, with a Ka of 10^-11, has a pKa of 11, which is closest to the desired pH of 9.5 among the given options.

Question 5

Assume an indicator works best when the equivalence point of a titration comes in the middle of the indicator range.Which indicator would be best for the following titration? 0.100 M HOCl (K_a = 3.5 $\times$ 10^-⁸)+ 0.100 M NaOH

Accepted Answer

The titration involves a strong base (NaOH) and a weak acid (HOCl). The equivalence point of the titration will occur when all of the HOCl has been converted to the conjugate base, OCl-. At this point, the solution will be basic. Thymolphthalein is a suitable indicator for this titration because its pH range (9.5 - 10.5) is close to the expected pH at the equivalence point (pH ~10). The indicator will change color as the solution becomes basic, indicating the end of the titration.

Question 6

A 50.00-mL solution of 0.0217 M butyric acid (K_a = 1.5 $\times$ 10^-⁵)is titrated with a 0.0302 M solution of sodium hydroxide as the titrant.What is the pH of at the equivalence point? (K_w = 1.00 $\times$ 10^-¹⁴)

Accepted Answer

At the equivalence point in the titration of a weak acid with a strong base, the solution contains the conjugate base of the weak acid in water. The pH is determined by the hydrolysis of the conjugate base, which is butyrate in this case. The pKa of butyric acid is given by -log(1.5 x 10^-5) = 4.82. Using the formula for the pH of a solution of a weak base, pH = 1/2(pKa + pKw - log C), where pKw = 14 at 25°C and C is the concentration of the conjugate base. The concentration of the conjugate base is equal to the initial concentration of the butyric acid because at the equivalence point, all the butyric acid has been converted to butyrate. Thus, pH = 1/2(4.82 + 14 + log 0.0217) = 8.46.

Question 7

Methyl orange is an indicator with a K_a of 1 $\times$10^-⁴.Its acid form,HIn,is red,while its base form,In^-,is yellow.At pH 6.0,the indicator will be

Accepted Answer

At pH 6.0, which is much higher than the pKa of methyl orange (around 3.7), the indicator will be in its base form, which is yellow.

Question 8

Consider the titration of 100.0 mL of the weak diprotic acid HS1U1B12S1U1B0A (0.10 M)with 0.20 M NaOH.What are the major species at each of the following points in the titration? (Water is always assumed to be a major species. )
-After 50.0 mL of 0.20 M NaOH is added

Accepted Answer

The answer of Consider the titration of 100.0 mL of...

Question 9

Consider the titration of 100.0 mL of the weak diprotic acid HS1U1B12S1U1B0A (0.10 M)with 0.20 M NaOH.What are the major species at each of the following points in the titration? (Water is always assumed to be a major species. )
-After 200.0 mL of 0.20 M NaOH is added

Accepted Answer

The answer of Consider the titration of 100.0 mL of...

Question 10

A certain indicator HIn has a pK_a of 9.00 and a color change becomes visible when 7.00% of it is In^-.At what pH is this color change visible?

Accepted Answer

The answer of A certain indicator HIn has a pK_a...

Question 11

Consider the titration of 100.0 mL of the weak diprotic acid HS1U1B12S1U1B0A (0.10 M)with 0.20 M NaOH.What are the major species at each of the following points in the titration? (Water is always assumed to be a major species. )
-Before any NaOH is added

Accepted Answer

Before any NaOH is added, the solution contains only the weak diprotic acid H₂A in its initial form, as no base has been introduced to start the deprotonation process.

Question 12

In the titration of a weak acid HA with 0.100 M NaOH,the stoichiometric point is known to occur at a pH value of approximately 10.Which of the following indicator acids would be best to use to mark the endpoint of this titration?

Accepted Answer

The best indicator for a titration is one whose pKa is close to the pH at the equivalence point. Since the pH at the stoichiometric point is approximately 10, the best choice is indicator B with a pKa of 11 (since pKa = -log(Ka)).

Question 13

Consider the titration of 100.0 mL of the weak diprotic acid HS1U1B12S1U1B0A (0.10 M)with 0.20 M NaOH.What are the major species at each of the following points in the titration? (Water is always assumed to be a major species. )
-After 75.0 mL of 0.20 M NaOH is added

Accepted Answer

At the point where 75.0 mL of 0.20 M NaOH has been added, the first proton of H₂A has been completely deprotonated, and the second proton is partially deprotonated. This means the major species present are the first deprotonation product (HA^-) and the second deprotonation product (A²^-), along with the partially deprotonated form.

Question 14

A 50.00-mL solution of 0.0350 M aniline (K_b = 3.8 $\times$10^-¹⁰)is titrated with a 0.0127 M solution of hydrochloric acid as the titrant.What is the pH at the equivalence point? (K_w = 1.0 $\times$10^-¹⁴)

Accepted Answer

The answer of A 50.00-mL solution of 0.0350 M aniline...

Quiz 15: Acid-Base Equilibria

Consider the titration of 100.0 mL of the weak diprotic acid H₂A (0.10 M) with 0.20 M NaOH.What are the major species at each of the following points in the titration? (Water is always assumed to be a major species. ) -After 25.0 mL of 0.20 M NaOH is added

In the titration of a weak acid HA with 0.100 M NaOH,the stoichiometric point is known to occur at a pH value of approximately 11.Which of the following indicators would be best to use to mark the endpoint of this titration?

A 50.00-mL solution of 0.0304 M ethanolamine (K_b = 3.2 $\times$ 10^-⁵) is titrated with a 0.0282 M solution of hydrochloric acid as the titrant.What is the pH of the base solution after 23.24 mL of titrant have been added? (K_w = 1.00 $\times$ 10^-¹⁴)

In the titration of a weak acid,HA,with a sodium hydroxide solution of approximately the same concentration,the stoichiometric point occurs at pH = 9.5.Which of the following weak acid indicators would be best suited to mark the endpoint of this titration?

Assume an indicator works best when the equivalence point of a titration comes in the middle of the indicator range.Which indicator would be best for the following titration? 0.100 M HOCl (K_a = 3.5 $\times$ 10^-⁸) + 0.100 M NaOH

A 50.00-mL solution of 0.0217 M butyric acid (K_a = 1.5 $\times$ 10^-⁵) is titrated with a 0.0302 M solution of sodium hydroxide as the titrant.What is the pH of at the equivalence point? (K_w = 1.00 $\times$ 10^-¹⁴)

Methyl orange is an indicator with a K_a of 1 $\times$ 10^-⁴.Its acid form,HIn,is red,while its base form,In^-,is yellow.At pH 6.0,the indicator will be

Consider the titration of 100.0 mL of the weak diprotic acid H₂A (0.10 M) with 0.20 M NaOH.What are the major species at each of the following points in the titration? (Water is always assumed to be a major species. ) -After 50.0 mL of 0.20 M NaOH is added

Consider the titration of 100.0 mL of the weak diprotic acid H₂A (0.10 M) with 0.20 M NaOH.What are the major species at each of the following points in the titration? (Water is always assumed to be a major species. ) -After 200.0 mL of 0.20 M NaOH is added

A certain indicator HIn has a pK_a of 9.00 and a color change becomes visible when 7.00% of it is In^-.At what pH is this color change visible?

Consider the titration of 100.0 mL of the weak diprotic acid H₂A (0.10 M) with 0.20 M NaOH.What are the major species at each of the following points in the titration? (Water is always assumed to be a major species. ) -Before any NaOH is added

In the titration of a weak acid HA with 0.100 M NaOH,the stoichiometric point is known to occur at a pH value of approximately 10.Which of the following indicator acids would be best to use to mark the endpoint of this titration?

Consider the titration of 100.0 mL of the weak diprotic acid H₂A (0.10 M) with 0.20 M NaOH.What are the major species at each of the following points in the titration? (Water is always assumed to be a major species. ) -After 75.0 mL of 0.20 M NaOH is added

A 50.00-mL solution of 0.0350 M aniline (K_b = 3.8 $\times$ 10^-¹⁰) is titrated with a 0.0127 M solution of hydrochloric acid as the titrant.What is the pH at the equivalence point? (K_w = 1.0 $\times$ 10^-¹⁴)

Quiz 15: Acid-Base Equilibria

Consider the titration of 100.0 mL of the weak diprotic acid H2A (0.10 M) with 0.20 M NaOH.What are the major species at each of the following points in the titration? (Water is always assumed to be a major species. ) -After 25.0 mL of 0.20 M NaOH is added

In the titration of a weak acid HA with 0.100 M NaOH,the stoichiometric point is known to occur at a pH value of approximately 11.Which of the following indicators would be best to use to mark the endpoint of this titration?

A 50.00-mL solution of 0.0304 M ethanolamine (Kb = 3.2 ×\times× 10-5) is titrated with a 0.0282 M solution of hydrochloric acid as the titrant.What is the pH of the base solution after 23.24 mL of titrant have been added? (Kw = 1.00 ×\times× 10-14)

In the titration of a weak acid,HA,with a sodium hydroxide solution of approximately the same concentration,the stoichiometric point occurs at pH = 9.5.Which of the following weak acid indicators would be best suited to mark the endpoint of this titration?

Assume an indicator works best when the equivalence point of a titration comes in the middle of the indicator range.Which indicator would be best for the following titration? 0.100 M HOCl (Ka = 3.5 ×\times× 10-8) + 0.100 M NaOH

A 50.00-mL solution of 0.0217 M butyric acid (Ka = 1.5 ×\times× 10-5) is titrated with a 0.0302 M solution of sodium hydroxide as the titrant.What is the pH of at the equivalence point? (Kw = 1.00 ×\times× 10-14)

Methyl orange is an indicator with a Ka of 1 ×\times× 10-4.Its acid form,HIn,is red,while its base form,In-,is yellow.At pH 6.0,the indicator will be

Consider the titration of 100.0 mL of the weak diprotic acid H2A (0.10 M) with 0.20 M NaOH.What are the major species at each of the following points in the titration? (Water is always assumed to be a major species. ) -After 50.0 mL of 0.20 M NaOH is added

Consider the titration of 100.0 mL of the weak diprotic acid H2A (0.10 M) with 0.20 M NaOH.What are the major species at each of the following points in the titration? (Water is always assumed to be a major species. ) -After 200.0 mL of 0.20 M NaOH is added

A certain indicator HIn has a pKa of 9.00 and a color change becomes visible when 7.00% of it is In-.At what pH is this color change visible?

Consider the titration of 100.0 mL of the weak diprotic acid H2A (0.10 M) with 0.20 M NaOH.What are the major species at each of the following points in the titration? (Water is always assumed to be a major species. ) -Before any NaOH is added

In the titration of a weak acid HA with 0.100 M NaOH,the stoichiometric point is known to occur at a pH value of approximately 10.Which of the following indicator acids would be best to use to mark the endpoint of this titration?

Consider the titration of 100.0 mL of the weak diprotic acid H2A (0.10 M) with 0.20 M NaOH.What are the major species at each of the following points in the titration? (Water is always assumed to be a major species. ) -After 75.0 mL of 0.20 M NaOH is added

A 50.00-mL solution of 0.0350 M aniline (Kb = 3.8 ×\times× 10-10) is titrated with a 0.0127 M solution of hydrochloric acid as the titrant.What is the pH at the equivalence point? (Kw = 1.0 ×\times× 10-14)

Consider the titration of 100.0 mL of the weak diprotic acid H₂A (0.10 M) with 0.20 M NaOH.What are the major species at each of the following points in the titration? (Water is always assumed to be a major species. ) -After 25.0 mL of 0.20 M NaOH is added

A 50.00-mL solution of 0.0304 M ethanolamine (K_b = 3.2 $\times$ 10^-⁵) is titrated with a 0.0282 M solution of hydrochloric acid as the titrant.What is the pH of the base solution after 23.24 mL of titrant have been added? (K_w = 1.00 $\times$ 10^-¹⁴)

Assume an indicator works best when the equivalence point of a titration comes in the middle of the indicator range.Which indicator would be best for the following titration? 0.100 M HOCl (K_a = 3.5 $\times$ 10^-⁸) + 0.100 M NaOH

A 50.00-mL solution of 0.0217 M butyric acid (K_a = 1.5 $\times$ 10^-⁵) is titrated with a 0.0302 M solution of sodium hydroxide as the titrant.What is the pH of at the equivalence point? (K_w = 1.00 $\times$ 10^-¹⁴)

Methyl orange is an indicator with a K_a of 1 $\times$ 10^-⁴.Its acid form,HIn,is red,while its base form,In^-,is yellow.At pH 6.0,the indicator will be

Consider the titration of 100.0 mL of the weak diprotic acid H₂A (0.10 M) with 0.20 M NaOH.What are the major species at each of the following points in the titration? (Water is always assumed to be a major species. ) -After 50.0 mL of 0.20 M NaOH is added

Consider the titration of 100.0 mL of the weak diprotic acid H₂A (0.10 M) with 0.20 M NaOH.What are the major species at each of the following points in the titration? (Water is always assumed to be a major species. ) -After 200.0 mL of 0.20 M NaOH is added

A certain indicator HIn has a pK_a of 9.00 and a color change becomes visible when 7.00% of it is In^-.At what pH is this color change visible?

Consider the titration of 100.0 mL of the weak diprotic acid H₂A (0.10 M) with 0.20 M NaOH.What are the major species at each of the following points in the titration? (Water is always assumed to be a major species. ) -Before any NaOH is added

Consider the titration of 100.0 mL of the weak diprotic acid H₂A (0.10 M) with 0.20 M NaOH.What are the major species at each of the following points in the titration? (Water is always assumed to be a major species. ) -After 75.0 mL of 0.20 M NaOH is added

A 50.00-mL solution of 0.0350 M aniline (K_b = 3.8 $\times$ 10^-¹⁰) is titrated with a 0.0127 M solution of hydrochloric acid as the titrant.What is the pH at the equivalence point? (K_w = 1.0 $\times$ 10^-¹⁴)