Question 1

Choose the correct statement.

Accepted Answer

This statement follows the concept of equivalent equivalents in acid-base neutralization reactions. One liter of 1 molar HCl contains 1 equivalent of acid, which will exactly neutralize 2 equivalents of base in 2 liters of 0.5 molar NaOH solution. The other statements contain errors, such as incorrect molarity or mole ratios, or use of an undefined compound.

Question 2

Which of the following can act as buffer solutions? I.0.1 M HC₂H₃O₂/0.1 M NaC₂H₃O₂ II.0.1 M NH₃/0.1 M NH₄Cl III.0.1 M HNO₃/0.1 M NaNO₃ IV.0.1 M H₂SO₃/0.1 M NaHSO₃ V.0.1 M KHSO₄/ 0.1 M H₂SO₄

Accepted Answer

Buffer solutions consist of a weak acid and its conjugate base or a weak base and its conjugate acid. Options I, II, and IV fit this description, as they involve combinations of weak acids/bases and their salts, which can resist changes in pH.

Question 3

An aqueous solution containing equimolar amounts of a weak acid with K_a = 10^-5 and its sodium salt has:

Accepted Answer

The answer of An aqueous solution containing equimolar amounts of...

Question 4

Phenol red indicator changes from yellow to red in the pH range from 6.6 to 8.0.State what color the indicator will assume in the following solution: 0.1 M NaCl(aq).

Accepted Answer

The answer of Phenol red indicator changes from yellow to...

Question 5

Phenol red indicator changes from yellow to red in the pH range from 6.6 to 8.0.State what color the indicator will assume in the following solution: 0.20 M KOH(aq).

Accepted Answer

Since KOH is a strong base, it will completely dissociate in water to form hydroxide ions (OH-) which will increase the pH of the solution. The pH will be above the range for which phenol red changes color, which means it will assume its red color to indicate the basic nature of the solution. Thus, the best choice is A) red.

Question 6

In the titration of 50.0 mL of 0.0200 M C₆H₅COOH(aq)with 0.100 M NaOH(aq),what is/are the major species in the solution after the addition of 5.0 mL of NaOH(aq)?

Accepted Answer

Before the equivalence point in a titration of a weak acid with a strong base, both the weak acid (C₆H₅COOH) and its conjugate base (C₆H₅COO-) will be present in the solution, along with the cation of the strong base (Na+).

Question 7

For the following titration,determine whether the solution at the equivalence point is acidic,basic or neutral and why: HCl(aq)is titrated with NH₃(aq)

Accepted Answer

The answer of For the following titration,determine whether the solution...

Question 8

What factor governs the selection of an indicator for a neutralization titration?

Accepted Answer

The selection of an indicator for a neutralization titration is primarily based on the pH at the stoichiometric (equivalence) point. The ideal indicator should have a pH value close to the equivalence point of the titration to give the most accurate results. This ensures that the indicator changes color at the same pH as the equivalence point, indicating the completion of the titration. Factors such as the final volume of the solution, volume of titrant, molarity of the standard solution, and solubility of the indicator are secondary considerations.

Question 9

The following compounds are available as 0.10 M aqueous solutions: pyridine (pK_b = 8.82),triethylamine (pK_b = 3.25),HClO₄,phenol (pK_a = 9.96),HClO (pK_a = 7.54),NH₃ (pK_b = 4.74)and NaOH.Identify two solutions that could be used to prepare a buffer with a pH of approximately 5.

Accepted Answer

Pyridine (a weak base) and HClO4 (a strong acid) can form a buffer solution with a pH around 5, as the pKa of pyridinium ion (conjugate acid of pyridine) is approximately 5.18.

Question 10

Which of the following mixtures would you dismiss as a potential buffer in a laboratory?

Accepted Answer

Buffers are solutions that resist changes in pH upon the addition of small amounts of acid or base. They are typically made from a weak acid and its conjugate base or a weak base and its conjugate acid. Choice A involves mixing a strong acid (HCl) with a salt, which does not form a buffer system because the strong acid will not allow for the establishment of an equilibrium between a weak acid and its conjugate base, which is necessary for buffer action.

Question 11

The Henderson-Hasselbach equation,used to calculate the pH of simple conjugate-pair buffer systems,would be expressed for an ammonia/ammonium chloride buffer,for which K_b(NH₃)is 1.8 × 10^-5,as:

Accepted Answer

The pH of an ammonia/ammonium buffer is calculated using the Henderson-Hasselbalch equation: pH = pKa + log([base]/[acid]). For ammonia, pKa = 14 - pKb = 14 - 4.75 = 9.25. Thus, the equation is pH = 9.25 + log([NH3]/[NH4+]).

Question 12

Which condition characterizes the stoichiometric point of a neutralization titration?

Accepted Answer

The stoichiometric point of a neutralization titration is where equivalent amounts of acid and base have reacted. At this point, all of the acid has been neutralized by the base and vice versa, with no excess titrant present. The pH may or may not be exactly 7.0, and the indicator may or may not have changed color, depending on the specific titration and indicator used.

Question 13

Phenol red indicator changes from yellow to red in the pH range from 6.6 to 8.0.State what color the indicator will assume in the following solution: 0.10 M NaCN(aq).

Accepted Answer

NaCN is a salt of a weak acid (HCN) and a strong base (NaOH), so it will create a basic solution. The pH of a 0.10 M NaCN solution is likely to be above 8.0, causing phenol red to turn red.

Question 14

Phenol red indicator changes from yellow to red in the pH range from 6.6 to 8.0.State what color the indicator will assume in the following solution: 0.10 M NH₄NO₃(aq).

Accepted Answer

0.10 M NH₄NO₃ is a solution of a weak base (NH₄⁺) and a strong acid (NO₃⁻), which results in an acidic solution with a pH less than 7. Therefore, phenol red will be yellow in this solution.

Question 15

The solution that is added from the buret during a titration is the:

Accepted Answer

The solution added from the buret during a titration is called the titrant. This is the solution that is used to react with the analyte in order to determine its concentration. The buret is used to accurately measure and dispense the titrant in controlled increments, allowing the titration to proceed slowly and with precision.

Question 16

Which of the following statements correctly describe a typical titration curve for the titration of a strong acid by a strong base?
I.The beginning pH is low.
II.The pH change is slow until near the equivalence point.
III.At the equivalence point,pH changes by a large value.
IV.Beyond the equivalence point,pH rises rapidly.
V.The equivalence point would be at a pH less than 3.5.

Accepted Answer

The answer of Which of the following statements correctly describe...

Question 17

methyl orange: red at pH < 3.1: orange at pH 3.1-4.4: yellow-orange above pH 4.4 Litmus: red at pH < 4.5: purple at pH 4.5-8.3: blue above pH 8.3 Thymol blue: yellow at pH < 8.0: green at pH 8.0-9.6: blue above pH 9.6 Trinitrobenzene: colorless at pH < 12: yellow at pH 12.0-1: orange above pH 14.0 Which of the pH indicators from the list above would be most appropriate for the titration of 0.30 M aqueous acetic acid (K_a = 1.8 × 10^-5)with 0.15 M aqueous sodium hydroxide?

Accepted Answer

Thymol blue would be the most appropriate pH indicator for the titration of acetic acid with sodium hydroxide because the equivalence point of the titration occurs at pH 8.2, which is within the pH range at which thymol blue changes color (pH 8.0-9.6). Methyl orange would change color at a lower pH and trinitrobenzene would change color at a much higher pH, while litmus would not provide a sharp color change at the equivalence point.

Question 18

Phenolphthalein may be used as an indicator for the titration of:

Accepted Answer

Phenolphthalein is a suitable indicator for the titration of a weak acid with a strong base. This is because the pH at the equivalence point of this titration is around 8.2, which is within the range of the color change of phenolphthalein (pink to colorless). Phenolphthalein is not suitable for the titration of strong acids or bases with each other, as the change in pH at the equivalence point is too small to be detected by phenolphthalein. It is also not suitable for the titration of weak bases with strong acids, as the pH at the equivalence point is too low for phenolphthalein to show a color change.

Question 19

Phenol red indicator changes from yellow to red in the pH range from 6.6 to 8.0.State what color the indicator will assume in the following solution: 0.10 M HC₂H₃O₂(aq).

Accepted Answer

We cannot determine the pH of the solution based on the given information, so we cannot use the pH range of the indicator. However, phenol red indicator changes from yellow to red in the pH range from 6.6 to 8.0, which indicates that it is yellow at a lower pH and red at a higher pH. The formula given does not contain any hydroxide ions, so the solution is acidic. Therefore, the indicator will assume its original color which is yellow.

Question 20

What is the buffer range (for an effective 2.0 pH unit)for a benzoic acid/sodium benzoate buffer? [Ka for benzoic acid is 6.3 × 10^-5]

Accepted Answer

The answer of What is the buffer range (for an...

Quiz 17: Additional Aspects of Acidbase Equilibria

Choose the correct statement.

Which of the following can act as buffer solutions? I.0.1 M HC₂H₃O₂/0.1 M NaC₂H₃O₂ II.0.1 M NH₃/0.1 M NH₄Cl III.0.1 M HNO₃/0.1 M NaNO₃ IV.0.1 M H₂SO₃/0.1 M NaHSO₃ V.0.1 M KHSO₄/ 0.1 M H₂SO₄

An aqueous solution containing equimolar amounts of a weak acid with K_a = 10^-5 and its sodium salt has:

Phenol red indicator changes from yellow to red in the pH range from 6.6 to 8.0.State what color the indicator will assume in the following solution: 0.1 M NaCl(aq) .

Phenol red indicator changes from yellow to red in the pH range from 6.6 to 8.0.State what color the indicator will assume in the following solution: 0.20 M KOH(aq) .

In the titration of 50.0 mL of 0.0200 M C₆H₅COOH(aq) with 0.100 M NaOH(aq) ,what is/are the major species in the solution after the addition of 5.0 mL of NaOH(aq) ?

For the following titration,determine whether the solution at the equivalence point is acidic,basic or neutral and why: HCl(aq) is titrated with NH₃(aq)

What factor governs the selection of an indicator for a neutralization titration?

The following compounds are available as 0.10 M aqueous solutions: pyridine (pK_b = 8.82) ,triethylamine (pK_b = 3.25) ,HClO₄,phenol (pK_a = 9.96) ,HClO (pK_a = 7.54) ,NH₃ (pK_b = 4.74) and NaOH.Identify two solutions that could be used to prepare a buffer with a pH of approximately 5.

Which of the following mixtures would you dismiss as a potential buffer in a laboratory?

The Henderson-Hasselbach equation,used to calculate the pH of simple conjugate-pair buffer systems,would be expressed for an ammonia/ammonium chloride buffer,for which K_b(NH₃) is 1.8 × 10^-5,as:

Which condition characterizes the stoichiometric point of a neutralization titration?

Phenol red indicator changes from yellow to red in the pH range from 6.6 to 8.0.State what color the indicator will assume in the following solution: 0.10 M NaCN(aq) .

Phenol red indicator changes from yellow to red in the pH range from 6.6 to 8.0.State what color the indicator will assume in the following solution: 0.10 M NH₄NO₃(aq) .

The solution that is added from the buret during a titration is the:

Phenolphthalein may be used as an indicator for the titration of:

Phenol red indicator changes from yellow to red in the pH range from 6.6 to 8.0.State what color the indicator will assume in the following solution: 0.10 M HC₂H₃O₂(aq) .

What is the buffer range (for an effective 2.0 pH unit) for a benzoic acid/sodium benzoate buffer? [Ka for benzoic acid is 6.3 × 10^-5]

Quiz 17: Additional Aspects of Acidbase Equilibria

Choose the correct statement.

Which of the following can act as buffer solutions? I.0.1 M HC2H3O2/0.1 M NaC2H3O2 II.0.1 M NH3/0.1 M NH4Cl III.0.1 M HNO3/0.1 M NaNO3 IV.0.1 M H2SO3/0.1 M NaHSO3 V.0.1 M KHSO4/ 0.1 M H2SO4

An aqueous solution containing equimolar amounts of a weak acid with Ka = 10-5 and its sodium salt has:

Phenol red indicator changes from yellow to red in the pH range from 6.6 to 8.0.State what color the indicator will assume in the following solution: 0.1 M NaCl(aq) .

Phenol red indicator changes from yellow to red in the pH range from 6.6 to 8.0.State what color the indicator will assume in the following solution: 0.20 M KOH(aq) .

In the titration of 50.0 mL of 0.0200 M C6H5COOH(aq) with 0.100 M NaOH(aq) ,what is/are the major species in the solution after the addition of 5.0 mL of NaOH(aq) ?

For the following titration,determine whether the solution at the equivalence point is acidic,basic or neutral and why: HCl(aq) is titrated with NH3(aq)

What factor governs the selection of an indicator for a neutralization titration?

The following compounds are available as 0.10 M aqueous solutions: pyridine (pKb = 8.82) ,triethylamine (pKb = 3.25) ,HClO4,phenol (pKa = 9.96) ,HClO (pKa = 7.54) ,NH3 (pKb = 4.74) and NaOH.Identify two solutions that could be used to prepare a buffer with a pH of approximately 5.

Which of the following mixtures would you dismiss as a potential buffer in a laboratory?

The Henderson-Hasselbach equation,used to calculate the pH of simple conjugate-pair buffer systems,would be expressed for an ammonia/ammonium chloride buffer,for which Kb(NH3) is 1.8 × 10-5,as:

Which condition characterizes the stoichiometric point of a neutralization titration?

Phenol red indicator changes from yellow to red in the pH range from 6.6 to 8.0.State what color the indicator will assume in the following solution: 0.10 M NaCN(aq) .

Phenol red indicator changes from yellow to red in the pH range from 6.6 to 8.0.State what color the indicator will assume in the following solution: 0.10 M NH4NO3(aq) .

The solution that is added from the buret during a titration is the:

Phenolphthalein may be used as an indicator for the titration of:

Phenol red indicator changes from yellow to red in the pH range from 6.6 to 8.0.State what color the indicator will assume in the following solution: 0.10 M HC2H3O2(aq) .

What is the buffer range (for an effective 2.0 pH unit) for a benzoic acid/sodium benzoate buffer? [Ka for benzoic acid is 6.3 × 10-5]

Which of the following can act as buffer solutions? I.0.1 M HC₂H₃O₂/0.1 M NaC₂H₃O₂ II.0.1 M NH₃/0.1 M NH₄Cl III.0.1 M HNO₃/0.1 M NaNO₃ IV.0.1 M H₂SO₃/0.1 M NaHSO₃ V.0.1 M KHSO₄/ 0.1 M H₂SO₄

An aqueous solution containing equimolar amounts of a weak acid with K_a = 10^-5 and its sodium salt has:

In the titration of 50.0 mL of 0.0200 M C₆H₅COOH(aq) with 0.100 M NaOH(aq) ,what is/are the major species in the solution after the addition of 5.0 mL of NaOH(aq) ?

For the following titration,determine whether the solution at the equivalence point is acidic,basic or neutral and why: HCl(aq) is titrated with NH₃(aq)

The following compounds are available as 0.10 M aqueous solutions: pyridine (pK_b = 8.82) ,triethylamine (pK_b = 3.25) ,HClO₄,phenol (pK_a = 9.96) ,HClO (pK_a = 7.54) ,NH₃ (pK_b = 4.74) and NaOH.Identify two solutions that could be used to prepare a buffer with a pH of approximately 5.

The Henderson-Hasselbach equation,used to calculate the pH of simple conjugate-pair buffer systems,would be expressed for an ammonia/ammonium chloride buffer,for which K_b(NH₃) is 1.8 × 10^-5,as:

Phenol red indicator changes from yellow to red in the pH range from 6.6 to 8.0.State what color the indicator will assume in the following solution: 0.10 M NH₄NO₃(aq) .

Phenol red indicator changes from yellow to red in the pH range from 6.6 to 8.0.State what color the indicator will assume in the following solution: 0.10 M HC₂H₃O₂(aq) .

What is the buffer range (for an effective 2.0 pH unit) for a benzoic acid/sodium benzoate buffer? [Ka for benzoic acid is 6.3 × 10^-5]