Question 1

In 0.100 M HC₂H₃O₂(aq), [H₃O+(aq)] = [C₂H₃O₂^-(aq)] = 1.3 x 10^-3 M. If a few drops of concentrated HCl(aq) are added to this solution, the C₂H₃O₂^-(aq) concentration is: A) < 1.3 x 10^-3 M B) > 1.3 x 10^-3 M C) = 1.3 x 10^-3M D) 0.100 M

Accepted Answer

Adding concentrated HCl will increase the concentration of H+ ions in the solution, leading to the protonation of H₃O- and C₂H₃O₂^-, producing more H2₃O and HC₂H₃O₂. As a result, the concentration of H₃O- and C₂H₃O₂^- will decrease. Therefore, the correct answer is A, the concentration of C₂H₃O₂^- will be less than 1.3 x 10^-3 M.

Question 2

The pH of a buffer solution changes only slightly with addition of a small amount of acid or base.

Accepted Answer

A buffer solution is a solution that resists change in pH upon addition of small amounts of an acid or base. It consists of a weak acid or base and its conjugate base or acid, respectively. The weak acid or base reacts with the added acid or base to prevent drastic changes in pH. This property is why buffer solutions are important in many biological and chemical processes.

Question 3

In the titration of a solution of HCN(aq) with NaOH(aq), the equivalence point occurs at a pH greater than 7.

Accepted Answer

HCN is a weak acid and NaOH is a strong base. At the equivalence point, all the HCN will be converted into its conjugate base (CN-), resulting in a basic solution with a pH greater than 7.

Question 4

What is the [HS1U1B13S1U1B0OS1U1P1+S1S1P0] of a solution measured to be 0.20 M in sodium acetate and 0.40 M in acetic acid? [Ka = 1.8 × 10S1U1P1-5S1S1P0]
A) 1.8 × 10S1U1P1-5S1S1P0 M
B) 9.0 × 10S1U1P1-6S1S1P0M
C) 3.6 × 10S1U1P1-5S1S1P0 M
D) 7.2 × 10S1U1P1-5S1S1P0M
E) 4.7 M

Accepted Answer

HS1U1B13S1U1B0O + H2S1U1P1O → S1U1B13S1U1B0OS1U1P1O + H2O

Initial: 0.40 M       0 M
Change: -x             +x
Equilibrium: 0.40 - x   x

Ka = [S1U1B13S1U1B0OS1U1P1O][H2O]/[HS1U1B13S1U1B0O]

1.8 × 10S1U1P1-5S1S1P0 = (x)(x)/(0.40 - x)

Ignoring x in the denominator gives:

1.8 × 10S1U1P1-5S1S1P0 = xS1U1P1O

x = 3.6 × 10S1U1P1-5S1S1P0 M

Therefore, [HS1U1B13S1U1B0O] = 0.40 - x = 0.40 - 3.6 × 10S1U1P1-5S1S1P0 = 0.40 M - 0.000036 M = 0.399964 M

The [HS1U1B13S1U1B0OS1U1P1+] concentration can be calculated using the equation:

[HS1U1B13S1U1B0OS1U1P1+] = Ka[H2S1U1P1O]/[HS1U1B13S1U1B0O] = (1.8 × 10S1U1P1-5S1S1P0)(0.000036)/0.399964 = 1.62 × 10S1U1P1-6S1S1P0

Therefore, the [HS1U1B13S1U1B0OS1U1P1+] concentration is 1.62 × 10S1U1P1-6S1S1P0 M, which corresponds to choice C.

Question 5

Which among the following pairs is inefficient as buffer pair?
A) ammonium chloride and ammonium hydroxide
B) sodium chloride and sodium hydroxide
C) boric acid and sodium borate
D) potassium carbonate and potassium bicarbonate
E) potassium bromide and hydrobromic acid

Accepted Answer

E  Sodium chloride and sodium hydroxide do not form a buffer as they do not consist of a weak acid and its conjugate base or a weak base and its conjugate acid. Potassium bromide and hydrobromic acid also do not form a buffer as hydrobromic acid is a strong acid, not a weak one.

Question 6

A salt of a polyprotic acid such as NaHCO₃ cannot act as an acid.

Accepted Answer

A salt of a polyprotic acid can act as an acid. NaHCO₃ is the salt of a polyprotic acid (H2CO₃), and can act as an acid in certain conditions, such as in the presence of a stronger base.

Question 7

The color change range of most acid-base indicators is 1 pH unit.

Accepted Answer

The answer of The color change range of most acid-base...

Question 8

The common ion in a mixture of a weak acid and a strong acid is the hydronium ion.

Accepted Answer

The common ion in a mixture of a weak acid and a strong acid is the hydronium ion, which is a common acidic ion in aqueous solutions. This is because both the weak acid and the strong acid will release hydronium ions when dissolved in water.

Question 9

How will addition of sodium acetate to an acetic acid solution affect the pH?
A) It will lower the pH.
B) The pH will not change.
C) The solution becomes hotter.
D) The pH cannot be measured.
E) It will raise the pH.

Accepted Answer

Sodium acetate is a salt formed from the reaction between acetic acid and sodium hydroxide. When it is added to an acetic acid solution, it acts as a buffer, meaning it can resist changes in the pH of the solution. Specifically, sodium acetate will react with any additional acid or base that is added to the solution, producing more acetic acid or acetate ions, respectively. This reaction helps to maintain the pH in the solution, and often leads to a slight increase in pH due to the production of acetate ions. Therefore, the answer is E, it will raise the pH.

Question 10

Acid-base indicators have two forms: an acid of one color and a base of another color.

Accepted Answer

Acid-base indicators are substances that change color depending on whether they are in an acidic or basic environment. They have two forms: the acidic form, which has one color, and the basic form, which has another color.

Question 11

How will addition of sodium chloride affect the pH of a HCl solution?
A) It will lower the pH.
B) The pH will not change.
C) The solution becomes hotter.
D) The pH cannot be measured.
E) It will raise the pH.

Accepted Answer

Adding sodium chloride (NaCl) to a hydrochloric acid (HCl) solution will not affect the pH as NaCl is a neutral salt and does not contribute any acidic or basic properties to the solution. Therefore, the pH will remain the same.

Question 12

For an accurate titration, the end point needs to match the equivalence point.

Accepted Answer

The end point of a titration refers to the point at which the indicator used changes color, indicating that the reaction has reached completion. The equivalence point, on the other hand, refers to the point at which the moles of the titrant (the solution added to the analyte) exactly match the moles of the analyte being titrated. In order for the titration to be accurate, the end point needs to match the equivalence point, indicating that the reaction has gone to completion and the correct amount of titrant has been added.

Question 13

The common ion in a mixture of a weak base and a strong base is the hydronium ion.

Accepted Answer

The common ion in a mixture of a weak base and a strong base is the hydroxide ion.

Question 14

A weak acid-strong base will produce a longer vertical section of a titration curve than will a strong acid-strong base.

Accepted Answer

The answer of A weak acid-strong base will produce a...

Question 15

What is the concentration of the acetate ion of a solution measured to be 0.20 M acetic acid and 0.20 M in hydrochloric acid? [Ka for acetic acid = 1.8 × 10^-5] A) 3.6 × 10^-5 M B) 9.0 × 10^-6M C) 1.8 × 10^-5 M D) 7.2 × 10^-5M E) 0.20 M

Accepted Answer

In the presence of a strong acid like HCl, the dissociation of acetic acid is suppressed. The concentration of acetate ion is approximately equal to the Ka of acetic acid, which is 1.8 × 10^-5 M.

Question 16

A strong acid and its conjugate base will form a buffer.

Accepted Answer

A buffer is typically formed by a weak acid and its conjugate base, not a strong acid, because strong acids completely dissociate in solution and do not provide the necessary equilibrium to resist changes in pH.

Question 17

The pH of a buffer depends mainly on the pKa of the weak acid component of the buffer.

Accepted Answer

The pH of a buffer is determined by the equilibrium constant for the dissociation of the weak acid, i.e. the pKa value. Therefore, the buffer pH is mainly dependent on the pKa of the weak acid component of the buffer.

Question 18

Ten milliliters of 0.10 M NH₃(aq) (K = 1.8 × 10^-5) is mixed with 10 mL of 0.10 M NH₄Cl. Neglecting the differences between activities and concentrations, the resulting solution: A) has a pH = 4.74 B) has a [H⁺] of approximately 10^-3 M C) has a [NH₄⁺] greater than that of the NH₄Cl(aq) D) has an [OH-] of 1.8 × 10^-5 M E) is acidic

Accepted Answer

The answer of Ten milliliters of 0.10 M NH₃(aq) (K...

Question 19

If some NH₄Cl is added to an aqueous solution of NH₃: A) the pH of the solution will increase B) the pH of the solution will decrease C) the solution will not have pH D) the pH of the solution will not change E) NH₄Cl cannot be added to NH₃

Accepted Answer

Adding NH4Cl to an NH3 solution introduces NH4+ ions, which can donate protons (H+) to the solution, thus increasing the concentration of H+ ions and decreasing the pH.

Question 20

A solution of sodium carbonate is easier to calculate the pH than sodium hydrogen carbonate because there is only one hydrolysis reaction instead of two.

Accepted Answer

Sodium carbonate, Na2CO3, undergoes hydrolysis to form one hydroxide ion and one carbonate ion, resulting in a basic solution. Sodium hydrogen carbonate, NaHCO3, undergoes two hydrolysis reactions, first forming one hydroxide ion and one bicarbonate ion, then the bicarbonate ion further hydrolyzing to form one more hydroxide ion and one carbonic acid molecule, resulting in a more complex pH calculation.

Quiz 17: Additional Aspects of Acid-Base Equilibria

In 0.100 M HC₂H₃O₂(aq) , [H₃O+(aq) ] = [C₂H₃O₂^-(aq) ] = 1.3 x 10^-3 M. If a few drops of concentrated HCl(aq) are added to this solution, the C₂H₃O₂^-(aq) concentration is:

The pH of a buffer solution changes only slightly with addition of a small amount of acid or base.

In the titration of a solution of HCN(aq) with NaOH(aq), the equivalence point occurs at a pH greater than 7.

What is the [H₃O⁺] of a solution measured to be 0.20 M in sodium acetate and 0.40 M in acetic acid? [Ka = 1.8 × 10^-5]

Which among the following pairs is inefficient as buffer pair?

A salt of a polyprotic acid such as NaHCO₃ cannot act as an acid.

The color change range of most acid-base indicators is 1 pH unit.

The common ion in a mixture of a weak acid and a strong acid is the hydronium ion.

How will addition of sodium acetate to an acetic acid solution affect the pH?

Acid-base indicators have two forms: an acid of one color and a base of another color.

How will addition of sodium chloride affect the pH of a HCl solution?

For an accurate titration, the end point needs to match the equivalence point.

The common ion in a mixture of a weak base and a strong base is the hydronium ion.

A weak acid-strong base will produce a longer vertical section of a titration curve than will a strong acid-strong base.

What is the concentration of the acetate ion of a solution measured to be 0.20 M acetic acid and 0.20 M in hydrochloric acid? [Ka for acetic acid = 1.8 × 10^-5]

A strong acid and its conjugate base will form a buffer.

The pH of a buffer depends mainly on the pKa of the weak acid component of the buffer.

Ten milliliters of 0.10 M NH₃(aq) (K = 1.8 × 10^-5) is mixed with 10 mL of 0.10 M NH₄Cl. Neglecting the differences between activities and concentrations, the resulting solution:

If some NH₄Cl is added to an aqueous solution of NH₃:

A solution of sodium carbonate is easier to calculate the pH than sodium hydrogen carbonate because there is only one hydrolysis reaction instead of two.

Quiz 17: Additional Aspects of Acid-Base Equilibria

In 0.100 M HC2H3O2(aq) , [H3O+(aq) ] = [C2H3O2-(aq) ] = 1.3 x 10-3 M. If a few drops of concentrated HCl(aq) are added to this solution, the C2H3O2-(aq) concentration is:

The pH of a buffer solution changes only slightly with addition of a small amount of acid or base.

In the titration of a solution of HCN(aq) with NaOH(aq), the equivalence point occurs at a pH greater than 7.

What is the [H3O+] of a solution measured to be 0.20 M in sodium acetate and 0.40 M in acetic acid? [Ka = 1.8 × 10-5]

Which among the following pairs is inefficient as buffer pair?

A salt of a polyprotic acid such as NaHCO3 cannot act as an acid.

The color change range of most acid-base indicators is 1 pH unit.

The common ion in a mixture of a weak acid and a strong acid is the hydronium ion.

How will addition of sodium acetate to an acetic acid solution affect the pH?

Acid-base indicators have two forms: an acid of one color and a base of another color.

How will addition of sodium chloride affect the pH of a HCl solution?

For an accurate titration, the end point needs to match the equivalence point.

The common ion in a mixture of a weak base and a strong base is the hydronium ion.

A weak acid-strong base will produce a longer vertical section of a titration curve than will a strong acid-strong base.

What is the concentration of the acetate ion of a solution measured to be 0.20 M acetic acid and 0.20 M in hydrochloric acid? [Ka for acetic acid = 1.8 × 10-5]

A strong acid and its conjugate base will form a buffer.

The pH of a buffer depends mainly on the pKa of the weak acid component of the buffer.

Ten milliliters of 0.10 M NH3(aq) (K = 1.8 × 10-5) is mixed with 10 mL of 0.10 M NH4Cl. Neglecting the differences between activities and concentrations, the resulting solution:

If some NH4Cl is added to an aqueous solution of NH3:

A solution of sodium carbonate is easier to calculate the pH than sodium hydrogen carbonate because there is only one hydrolysis reaction instead of two.

In 0.100 M HC₂H₃O₂(aq) , [H₃O+(aq) ] = [C₂H₃O₂^-(aq) ] = 1.3 x 10^-3 M. If a few drops of concentrated HCl(aq) are added to this solution, the C₂H₃O₂^-(aq) concentration is:

What is the [H₃O⁺] of a solution measured to be 0.20 M in sodium acetate and 0.40 M in acetic acid? [Ka = 1.8 × 10^-5]

A salt of a polyprotic acid such as NaHCO₃ cannot act as an acid.

What is the concentration of the acetate ion of a solution measured to be 0.20 M acetic acid and 0.20 M in hydrochloric acid? [Ka for acetic acid = 1.8 × 10^-5]

Ten milliliters of 0.10 M NH₃(aq) (K = 1.8 × 10^-5) is mixed with 10 mL of 0.10 M NH₄Cl. Neglecting the differences between activities and concentrations, the resulting solution:

If some NH₄Cl is added to an aqueous solution of NH₃: