Question 1

Sodium hypochlorite is a common ingredient in household bleach. What is the pH of this bleach if It contains 5% NaOCl by mass? (pK_a of HOCl = 7.46)

Accepted Answer

First, we need to write the balanced equation for the reaction that occurs when NaOCl dissolves in water:
NaOCl + H2O ↔ HOCl + Na+ + OH-
Since bleach contains 5% NaOCl by mass, we can assume that the solution is approximately 5% NaOCl by weight. To find the concentration of NaOCl in moles per liter (M), we need to divide the percent mass by the molecular weight of NaOCl:
5% NaOCl = 5 g NaOCl / 100 g solution
Molecular weight of NaOCl = 74.44 g/mol
5 g NaOCl / 74.44 g/mol = 0.067 M NaOCl
Next, we need to determine the pH of the solution. We know that when NaOCl dissolves, it forms HOCl and OH-. The pH of the solution depends on the relative concentrations of these two species. To calculate the pH, we need to use the pKa of HOCl:
pKa = 7.46
pH = pKa + log([HOCl]/[OCl-])
We can assume that the concentration of Na+ is negligible and does not affect the pH. Therefore,
[OCl-] = 0.067 M
[HOCl] = Kw /[OH-] = 1.0 x 10^-14 / [OH-]
Substituting these values into the equation for pH,
pH = 7.46 + log([1.0 x 10^-14]/[0.067 x OH-])
pH = 7.5 + log(1.5 x 10^-13/[OH-])
pH = 7.5 - 12.8 + log(1/[OH-])
pH = -5.3 + log(1/[OH-])
pH = -5.3 - log([OH-])
pH = -5.3 - log(5.9 x 10^13)
pH = 11.3
Therefore, the pH of bleach containing 5% NaOCl by mass is approximately 11.

Question 2

Identify the weakest and strongest acids in the group below. The weakest acid is listed first in the responses. H₂O, H₂S, H₂Se

Accepted Answer

The answer of Identify the weakest and strongest acids in...

Question 3

In each of the following, the stronger acid is identified and an explanation is given. All except one are correct statements. Which one is not correct?

Accepted Answer

The answer of In each of the following, the stronger...

Question 4

Which ending to the statement is not correct? The weak acid HY will be stronger than the weak acid HZ if ________

Accepted Answer

The strength of a weak acid is influenced by the stability of its conjugate base, which is affected by factors such as resonance, electronegativity, and the number of oxygen atoms. The presence of Br instead of Cl (choice E) does not necessarily make HY a stronger acid than HZ, as electronegativity and size differences between Br and Cl do not directly correlate to acid strength in the context provided.

Question 5

Which one of the following statements is not correct?

Accepted Answer

The answer of Which one of the following statements is...

Question 6

The degree of ionization of a strong acid is ________

Accepted Answer

A strong acid completely dissociates in water, meaning that all of the acid molecules ionize to form ions. Therefore, the degree of ionization is 100%.

Question 7

Identify the weakest and strongest acids in the group below. The weakest acid is listed first in the responses. HClO₄, HClO₂, HClO₃

Accepted Answer

The answer of Identify the weakest and strongest acids in...

Question 8

What is the hydronium ion concentration of a 0.20 M solution of ammonia? The K_b value for ammonia is 1.8 *10^-⁵.

Accepted Answer

The answer of What is the hydronium ion concentration of...

Question 9

Identify the weakest and strongest acids in the group below. The weakest acid is listed first in the responses. H₂Te, H₂S, H₂Se

Accepted Answer

The answer of Identify the weakest and strongest acids in...

Question 10

Identify the weakest and strongest acids in the group below. The weakest acid is listed first in the responses.
HOCl, HOBr, HOI

Accepted Answer

The acidity of hypohalous acids (HOX) increases with the electronegativity of the halogen. Iodine is the least electronegative, making HOI the weakest acid, while chlorine is the most electronegative, making HOCl the strongest acid.

Question 11

Identify the weakest and strongest acids in the group below. The weakest acid is listed first in the responses. HCl, H₂S, PH₃

Accepted Answer

PH₃ is the weakest acid and HCl is the strongest acid among the given options.

Question 12

What is the pH of a 0.20 M solution of ammonia? The K_b value for ammonia is 1.8 * 10^-⁵.

Accepted Answer

Ammonia is a weak base, and its pH can be calculated using the formula for Kb. First, calculate the concentration of OH- ions using the formula: [OH-] = √(Kb * [NH3]). Then, calculate the pOH and subtract it from 14 to find the pH. The calculation gives a pH of approximately 11.28.

Question 13

The degree of ionization of a weak acid ________
I. varies with the concentration of the acid.
II. depends on which weak acid it is.
III. is 100%.
IV. is greater than 50% but less than 100%.

Accepted Answer

The degree of ionization of a weak acid varies with its concentration (the more diluted the acid, the higher the degree of ionization) and depends on the nature of the acid itself (different weak acids have different ionization constants). It is not 100% nor is it typically greater than 50% but less than 100%, as weak acids do not fully ionize in solution.

Question 14

The analysis label on a 500 mL bottle of Fiji natural artesian water reports pH = 7.5 and 140 mg of bicarbonates, HCO₃^-. Calculate the pH expected as a result of the bicarbonates to see if these two numbers are consistent with each other. (K_b = 2.4 * 10^-⁸ for HCO₃^-)

Accepted Answer

The answer of The analysis label on a 500 mL...

Question 15

Identify the weakest and strongest acids in the group below. The weakest acid is listed first in the responses. HClO, HClO₂, HClO₃

Accepted Answer

The answer of Identify the weakest and strongest acids in...

Question 16

The degree of ionization ________

Accepted Answer

The degree of ionization of a weak acid decreases as the concentration of the weak acid increases. This is because at higher concentrations, the acid molecules are closer together and can interact with each other, making it more difficult for them to dissociate into ions.

Question 17

Vitamin C, which is ascorbic acid, is a diprotic acid with $\mathrm { p } K _ { \mathrm { a }_{1} }$ = 5.00 and $\mathrm { p } K _ { \mathrm { s }_{2} }$
= 11.3. What is
The pH of a 0.125 M solution of ascorbic acid?

Accepted Answer

For a diprotic acid, the first dissociation is the most significant in determining pH. Using the formula for weak acid dissociation, $\mathrm{pH} = \frac{1}{2}(\mathrm{pK_a} - \log C)$, where C is the concentration, we find $\mathrm{pH} \approx 2.95$.

Question 18

A solution of the weak acid HF and a solution of the strong acid HCl have the same pH. Which solution will require the most sodium hydroxide, NaOH, to neutralize?

Accepted Answer

Although the pH of the two solutions is the same, the weak acid HF will require more NaOH to neutralize because it does not fully dissociate and therefore has a lower H+ concentration. This means that more NaOH is needed to neutralize the remaining H+ ions present in the solution. Therefore, choice B is correct.

Question 19

Identify the weakest and strongest acids in the group below. The weakest acid is listed first in the responses.
HCl, HBr, HI

Accepted Answer

The answer of Identify the weakest and strongest acids in...

Question 20

The pH of vinegar is 2.4, and the acetic acid in vinegar has a concentration of about 0.85 M. The pK_a of acetic acid is 4.75. What is the percent ionization of acetic acid in vinegar?

Accepted Answer

To find the percent ionization, we need to use the equation for the acid dissociation constant:

Ka = [H+][A-]/[HA]

Since vinegar is primarily composed of acetic acid and water, we can assume that the initial concentration of acetic acid is equal to the concentration of the acid remaining after dissociation:

[HA]0 = 0.85 M

Let x be the concentration of H+ produced by dissociation. Then the concentration of A- is also x. Therefore, the equilibrium concentration of HA is:

[HA] = [HA]0 - x
[HA] = 0.85 M - x

Plugging these values into the Ka expression and solving for x gives:

Ka = (x^2) / (0.85 - x) = 1.8 x 10^-5
x = 0.0021 M

The percent ionization is the ratio of the concentration of H+ produced by dissociation to the initial concentration of acetic acid, multiplied by 100:

% ionization = (0.0021 / 0.85) x 100 = 0.247%

Rounding to one significant figure gives answer C: 0.47%.

Quiz 16: Acid-Base and Solubility Equilibria: Reactions in Soil and Water

Sodium hypochlorite is a common ingredient in household bleach. What is the pH of this bleach if It contains 5% NaOCl by mass? (pKa of HOCl = 7.46)

Identify the weakest and strongest acids in the group below. The weakest acid is listed first in the responses. H2O, H2S, H2Se

In each of the following, the stronger acid is identified and an explanation is given. All except one are correct statements. Which one is not correct?

Which ending to the statement is not correct? The weak acid HY will be stronger than the weak acid HZ if ________

Which one of the following statements is not correct?

The degree of ionization of a strong acid is ________

Identify the weakest and strongest acids in the group below. The weakest acid is listed first in the responses. HClO4, HClO2, HClO3

What is the hydronium ion concentration of a 0.20 M solution of ammonia? The Kb value for ammonia is 1.8 *10-5.

Identify the weakest and strongest acids in the group below. The weakest acid is listed first in the responses. H2Te, H2S, H2Se

Identify the weakest and strongest acids in the group below. The weakest acid is listed first in the responses. HOCl, HOBr, HOI

Identify the weakest and strongest acids in the group below. The weakest acid is listed first in the responses. HCl, H2S, PH3

What is the pH of a 0.20 M solution of ammonia? The Kb value for ammonia is 1.8 * 10-5.

The degree of ionization of a weak acid ________ I. varies with the concentration of the acid. II. depends on which weak acid it is. III. is 100%. IV. is greater than 50% but less than 100%.

The analysis label on a 500 mL bottle of Fiji natural artesian water reports pH = 7.5 and 140 mg of bicarbonates, HCO3-. Calculate the pH expected as a result of the bicarbonates to see if these two numbers are consistent with each other. (Kb = 2.4 * 10-8 for HCO3-)

Identify the weakest and strongest acids in the group below. The weakest acid is listed first in the responses. HClO, HClO2, HClO3

The degree of ionization ________

Vitamin C, which is ascorbic acid, is a diprotic acid with pKa1\mathrm { p } K _ { \mathrm { a }_{1} }pKa1​​ = 5.00 and pKs2\mathrm { p } K _ { \mathrm { s }_{2} }pKs2​​ = 11.3. What is The pH of a 0.125 M solution of ascorbic acid?

A solution of the weak acid HF and a solution of the strong acid HCl have the same pH. Which solution will require the most sodium hydroxide, NaOH, to neutralize?

Identify the weakest and strongest acids in the group below. The weakest acid is listed first in the responses. HCl, HBr, HI

The pH of vinegar is 2.4, and the acetic acid in vinegar has a concentration of about 0.85 M. The pKa of acetic acid is 4.75. What is the percent ionization of acetic acid in vinegar?

Sodium hypochlorite is a common ingredient in household bleach. What is the pH of this bleach if It contains 5% NaOCl by mass? (pK_a of HOCl = 7.46)

Identify the weakest and strongest acids in the group below. The weakest acid is listed first in the responses. H₂O, H₂S, H₂Se

Identify the weakest and strongest acids in the group below. The weakest acid is listed first in the responses. HClO₄, HClO₂, HClO₃

What is the hydronium ion concentration of a 0.20 M solution of ammonia? The K_b value for ammonia is 1.8 *10^-⁵.

Identify the weakest and strongest acids in the group below. The weakest acid is listed first in the responses. H₂Te, H₂S, H₂Se

Identify the weakest and strongest acids in the group below. The weakest acid is listed first in the responses. HCl, H₂S, PH₃

What is the pH of a 0.20 M solution of ammonia? The K_b value for ammonia is 1.8 * 10^-⁵.

The analysis label on a 500 mL bottle of Fiji natural artesian water reports pH = 7.5 and 140 mg of bicarbonates, HCO₃^-. Calculate the pH expected as a result of the bicarbonates to see if these two numbers are consistent with each other. (K_b = 2.4 * 10^-⁸ for HCO₃^-)

Identify the weakest and strongest acids in the group below. The weakest acid is listed first in the responses. HClO, HClO₂, HClO₃

Vitamin C, which is ascorbic acid, is a diprotic acid with $\mathrm { p } K _ { \mathrm { a }_{1} }$ = 5.00 and $\mathrm { p } K _ { \mathrm { s }_{2} }$ = 11.3. What is The pH of a 0.125 M solution of ascorbic acid?

The pH of vinegar is 2.4, and the acetic acid in vinegar has a concentration of about 0.85 M. The pK_a of acetic acid is 4.75. What is the percent ionization of acetic acid in vinegar?