Question 1

Calculate the percent ionization of formic acid (HCO₂H) in a solution that is 0.311 M in formic acid and 0.189 M in sodium formate (NaHCO₂). The K_aof formic acid is 1.77 ×10^-⁴.

Accepted Answer

First, we need to write out the balanced chemical equation for the dissociation of formic acid: HCO₂H ⇌ H+ + CO₂- Next, we can use the given equilibrium constant (Ka) and the initial concentrations of formic acid and sodium formate to set up an ICE table: HCO₂H ⇌ H+ + CO₂- I 0.311 M 0 M 0 M C -x +x +x E 0.311-x x x The Ka of formic acid is equal to [H+][CO₂-]/[HCO₂H]. Substituting the equilibrium concentrations into this expression gives: 1.77 ×10^-⁴ = x^2 / (0.311 - x) We can make the assumption that x is much smaller than 0.311, so we can approximate 0.311 - x to be approximately 0.311: 1.77 ×10^-⁴ = x^2 / 0.311 Solving for x gives x = 0.0295 M. The percent ionization is equal to (x / 0.311) x 100%. Plugging in our calculated value for x gives: Percent ionization = (0.0295 / 0.311) x 100% = 9.52% Therefore, the best choice is A, 0.0952, as it is the closest value to our calculated value of 9.52%.

Question 2

The common- ion effect refers to the observation _ .

Accepted Answer

The common-ion effect refers to the observation that the addition of an ion that is already present in a solution can cause a shift in the equilibrium position. In the case of selective precipitation, the addition of a counterion that forms a compound with very low solubility can promote the precipitation of a metal ion. This is an example of the common-ion effect.

Question 3

Suppose you have just added 200.0 ml of a solution containing 0.5000 moles of acetic acid per liter to 100.0 ml of 0.5000 M NaOH. What is the final pH? The Ka of acetic acid is 1.770× 10^-⁵.

Accepted Answer

The answer of Suppose you have just added 200.0 ml...

Question 4

Calculate the pH of a buffer that contains 0.270 M hydrofluoric acid (HF) and 0.180 M cesium fluoride (CsF). The Ka of hydrofluoric acid is 6.80 × 10^-⁴.

Accepted Answer

The answer of Calculate the pH of a buffer that...

Question 5

Of the substances below, will decrease the solubility of Pb(OH)₂in a saturated solution.

Accepted Answer

Adding Pb(NO3)2 increases the concentration of Pb2+ ions in the solution, which shifts the equilibrium to the left according to Le Chatelier's principle, decreasing the solubility of Pb(OH)2.

Question 6

Which of the following could be added to a solution of acetic acid to prepare a buffer? sodium acetate sodium hydroxide nitric acid hydrofluoric acid

Accepted Answer

Sodium acetate or sodium hydroxide can be added to a solution of acetic acid to prepare a buffer. Sodium acetate will act as a conjugate base to the weak acid acetic acid, while sodium hydroxide will react with some of the acetic acid to form its conjugate base, acetate ion. Both sodium acetate and sodium hydroxide will help maintain the pH of the solution by absorbing any excess protons or hydroxide ions present. Nitric acid and hydrofluoric acid are strong acids, so they would only further acidify the solution and not act as a buffer.

Question 7

A solution containing which one of the following pairs of substances will be a buffer solution?

Accepted Answer

A buffer solution contains a weak acid and its conjugate base or a weak base and its conjugate acid. In option B, we have CsF, which is a weak base, and HF, which is a weak acid. Therefore, option B is the correct answer. The other options do not contain a weak acid and its conjugate base or a weak base and its conjugate acid.

Question 8

Calculate the pH of a solution that is 0.210 M in nitrous acid (HNO₂) and 0.290 M in potassium nitrite (KNO₂). The acid dissociation constant of nitrous acid is 4.50 × 10^-⁴.

Accepted Answer

The dissociation equation for nitrous acid is: HNO₂ ⇌ H+S1U1BONO₂- The acid dissociation constant, Ka, is given as 4.50 × 10^-. The expression for Ka is: Ka = [H+S1U1B][NO2-S1U1B]/[HNO₂] Since the solution contains both nitrous acid and its conjugate base (potassium nitrite), it is a buffer solution. The pH of a buffer solution can be calculated using the Henderson-Hasselbalch equation: pH = pKa + log([NO2-S1U1B]/[HNO₂]) Substituting the given values: pH = -log(4.50 × 10^-) + log([0.290]/[0.210]) pH = 3.490 Therefore, the correct answer is B.

Question 9

In which of the following aqueous solutions would you expect AgBr to have the lowest solubility?

Accepted Answer

The answer of In which of the following aqueous solutions...

Question 10

A 25.0 mL sample of 0.723 M HClO₄is titrated with a 0.273 M KOH solution. The H₃O⁺ concentration after the addition of 10.0 mL of KOH is M.

Accepted Answer

The balanced chemical equation for the reaction between HClO and KOH is:

HClO + KOH → KClO + H2O

This equation shows that for every mole of KOH used, one mole of HClO is consumed. Therefore, the number of moles of HClO initially present in the 25.0 mL sample is:

moles HClO = M × V = 0.723 mol/L × 0.0250 L = 0.0181 mol

When 10.0 mL of 0.273 M KOH is added, the number of moles of KOH added is:

moles KOH = M × V = 0.273 mol/L × 0.0100 L = 0.00273 mol

Since KOH and HClO react in a 1:1 ratio, the number of moles of HClO remaining after the addition of KOH is:

moles HClO remaining = moles HClO initially present - moles KOH added
moles HClO remaining = 0.0181 mol - 0.00273 mol = 0.0154 mol

The volume of the solution after the addition of KOH is:

final volume = initial volume + volume of KOH added
final volume = 25.0 mL + 10.0 mL = 35.0 mL = 0.0350 L

Therefore, the concentration of HClO remaining in the solution is:

[HClO] = moles HClO remaining / final volume
[HClO] = 0.0154 mol / 0.0350 L = 0.440 mol/L

So the answer is D: 0.440.

Question 11

What is the molar solubility of barium fluoride ( BaF₂) in water? The solubility- product constant for BaF₂is 1.7 × 10^-⁶at 25°C.

Accepted Answer

The answer of What is the molar solubility of barium...

Question 12

For which salt should the aqueous solubility be most sensitive to pH?

Accepted Answer

CaF₂ is the salt that should be most sensitive to pH because it is a weak acid salt. The solubility of CaF₂ will increase as the pH of the solution increases because the fluoride ion will be more soluble in a basic solution.

Question 13

The K_aof acetic acid is 1.76 × 10^-⁵. The pH of a buffer prepared by combining 50.0 mL of 1.00 M potassium acetate and 50.0 mL of 1.00 M acetic acid is _ .

Accepted Answer

To find the pH of a buffer, we need to use the Henderson-Hasselbalch equation:

pH = pKa + log([A-]/[HA])

where pKa is the dissociation constant of the weak acid, [A-] is the concentration of the conjugate base (in this case, potassium acetate), and [HA] is the concentration of the weak acid (acetic acid).

From the given information, we can find the pKa of acetic acid:

pKa = -log(Ka) = -log(1.76 × 10^-5) = 4.76

Next, we need to find the concentrations of [A-] and [HA] in the buffer solution. We know that we combined 50.0 mL of 1.00 M potassium acetate, so the moles of potassium acetate are:

n(A-) = 0.0500 L x 1.00 mol/L = 0.0500 mol

Assuming that potassium acetate dissociates completely to K+ and A-, the concentration of A- is also 0.0500 M.

For acetic acid, we need to take into account that it does not dissociate completely in solution. We can use the given Ka and the initial concentration of acetic acid to set up an ICE table:

Ka = [H+][A-]/[HA]
1.76 × 10^-5 = (x)(0.0500)/(0.0500 - x)

where x is the concentration of H+ and (0.0500 - x) is the concentration of undissociated acetic acid.

Solving for x, we get:

x = 8.55 × 10^-5

This concentration of H+ corresponds to a pH of:

pH = -log(H+) = -log(8.55 × 10^-5) = 4.07

To check our assumption that the concentration of undissociated acetic acid is negligible compared to the initial concentration of 1.00 M, we can calculate the percent dissociation:

% dissociation = ([H+] / initial [HA]) x 100
% dissociation = (8.55 × 10^-5 / 1.00) x 100
% dissociation = 0.00855 x 100 = 0.855%

This is a very low percent dissociation, so our assumption is valid.

Now we can use the Henderson-Hasselbalch equation to find the pH:

pH = pKa + log([A-]/[HA])
pH = 4.76 + log(0.0500/0.00855)
pH = 4.76 + 1.31
pH = 6.07

However, we need to remember that we calculated the pH of the acetic acid solution, not the buffer solution. To find the pH of the buffer, we need to take into account the dilution of the acetic acid by the potassium acetate:

moles of acetic acid = initial moles / dilution factor
moles of acetic acid = 0.0500 mol / 2
moles of acetic acid = 0.0250 mol

moles of potassium acetate = initial moles / dilution factor
moles of potassium acetate = 0.0500 mol / 2
moles of potassium acetate = 0.0250 mol

total volume of buffer solution = 50.0 mL + 50.0 mL = 0.1000 L

concentration of acetic acid in buffer = moles / volume
concentration of acetic acid in buffer = 0.0250 mol / 0.1000 L
concentration of acetic acid in buffer = 0.250 M

concentration of potassium acetate in buffer = moles / volume
concentration of potassium acetate in buffer = 0.0250 mol / 0.1000 L
concentration of potassium acetate in buffer = 0.250 M

Now we can use the Henderson-Hasselbalch equation to find the pH of the buffer:

pH = pKa + log([A-]/[HA])
pH = 4.76 + log(0.250/0.250)
pH = 4.76 + 0
pH = 4.76

Therefore, the answer is C) 4.77.

Question 14

Suppose you have just added 100.0 ml of a solution containing 0.5000 moles of acetic acid per liter to 400.0 ml of 0.5000 M NaOH. What is the final pH? The Ka of acetic acid is 1.770× 10^-⁵.

Accepted Answer

The answer of Suppose you have just added 100.0 ml...

Question 15

200.0 ml of a solution containing 0.5000 moles of acetic acid per liter is added to 200.0 ml of 0.5000 M NaOH. What is the final pH? The Ka of acetic acid is 1.770 × 10^-⁵.

Accepted Answer

The answer of 200.0 ml of a solution containing 0.5000...

Question 16

Calculate the percent ionization of formic acid (HCO₂H) in a solution that is 0.219 M in formic acid. The K_aof formic acid is 1.77 × 10^-⁴.

Accepted Answer

The answer of Calculate the percent ionization of formic acid...

Question 17

Calculate the pH of a buffer solution that contains 0.820 grams of sodium acetate and 0.01 moles of acetic acid in 100 ml of water. The Ka of acetic acid is 1.77 × 10^-⁵.

Accepted Answer

The answer of Calculate the pH of a buffer solution...

Question 18

Which of the following could be added to a solution of sodium acetate to produce a buffer? acetic acid hydrochloric acid potassium acetate sodium chloride

Accepted Answer

For a buffer to be formed, there must be a weak acid/conjugate base or weak base/conjugate acid pair present. In this case, adding acetic acid or hydrochloric acid to the sodium acetate solution will create a weak acid/conjugate base pair, forming a buffer. Therefore, choice D is the best answer.

Question 19

Which below best describe(s) the behavior of an amphoteric hydroxide in water?

Accepted Answer

Amphoteric hydroxides react with both acids and bases to form salts and water.

Question 20

What is the pH of a buffer solution that is 0.255 M in hypochlorous acid (HClO) and 0.333 M in sodium hypochlorite? The K_aof hypochlorous acid is 3.81 × 10^-⁸.

Accepted Answer

First, we need to write the equation for the ionization of HClO:
HClO ⇌ H+ + ClO-

Next, we need to find the pKa of HClO:
pKa = -log(Ka) = -log(3.81 × 10^-8) = 7.42

Using the Henderson-Hasselbalch equation:

pH = pKa + log([A-]/[HA])
pH = 7.42 + log(0.333/0.255)
pH = 7.54

Therefore, the pH of the buffer solution is 7.54, which is closest to answer choice B.

Quiz 17: Additional Aspects of Equilibria

Calculate the percent ionization of formic acid (HCO₂H) in a solution that is 0.311 M in formic acid and 0.189 M in sodium formate (NaHCO₂) . The K_aof formic acid is 1.77 ×10^-⁴.

The common- ion effect refers to the observation _ .

Suppose you have just added 200.0 ml of a solution containing 0.5000 moles of acetic acid per liter to 100.0 ml of 0.5000 M NaOH. What is the final pH? The Ka of acetic acid is 1.770× 10^-⁵.

Calculate the pH of a buffer that contains 0.270 M hydrofluoric acid (HF) and 0.180 M cesium fluoride (CsF). The Ka of hydrofluoric acid is 6.80 × 10^-⁴.

Of the substances below, will decrease the solubility of Pb(OH) ₂in a saturated solution.

Which of the following could be added to a solution of acetic acid to prepare a buffer? sodium acetate sodium hydroxide nitric acid hydrofluoric acid

A solution containing which one of the following pairs of substances will be a buffer solution?

Calculate the pH of a solution that is 0.210 M in nitrous acid (HNO₂) and 0.290 M in potassium nitrite (KNO₂) . The acid dissociation constant of nitrous acid is 4.50 × 10^-⁴.

In which of the following aqueous solutions would you expect AgBr to have the lowest solubility?

A 25.0 mL sample of 0.723 M HClO₄is titrated with a 0.273 M KOH solution. The H₃O⁺ concentration after the addition of 10.0 mL of KOH is M.

What is the molar solubility of barium fluoride ( BaF₂) in water? The solubility- product constant for BaF₂is 1.7 × 10^-⁶at 25°C.

For which salt should the aqueous solubility be most sensitive to pH?

The K_aof acetic acid is 1.76 × 10^-⁵. The pH of a buffer prepared by combining 50.0 mL of 1.00 M potassium acetate and 50.0 mL of 1.00 M acetic acid is _ .

Suppose you have just added 100.0 ml of a solution containing 0.5000 moles of acetic acid per liter to 400.0 ml of 0.5000 M NaOH. What is the final pH? The Ka of acetic acid is 1.770× 10^-⁵.

200.0 ml of a solution containing 0.5000 moles of acetic acid per liter is added to 200.0 ml of 0.5000 M NaOH. What is the final pH? The Ka of acetic acid is 1.770 × 10^-⁵.

Calculate the percent ionization of formic acid (HCO₂H) in a solution that is 0.219 M in formic acid. The K_aof formic acid is 1.77 × 10^-⁴.

Calculate the pH of a buffer solution that contains 0.820 grams of sodium acetate and 0.01 moles of acetic acid in 100 ml of water. The Ka of acetic acid is 1.77 × 10^-⁵.

Which of the following could be added to a solution of sodium acetate to produce a buffer? acetic acid hydrochloric acid potassium acetate sodium chloride

Which below best describe(s) the behavior of an amphoteric hydroxide in water?

What is the pH of a buffer solution that is 0.255 M in hypochlorous acid (HClO) and 0.333 M in sodium hypochlorite? The K_aof hypochlorous acid is 3.81 × 10^-⁸.

Quiz 17: Additional Aspects of Equilibria

Calculate the percent ionization of formic acid (HCO2H) in a solution that is 0.311 M in formic acid and 0.189 M in sodium formate (NaHCO2) . The Ka of formic acid is 1.77 ×10- 4.

The common- ion effect refers to the observation _ .

Suppose you have just added 200.0 ml of a solution containing 0.5000 moles of acetic acid per liter to 100.0 ml of 0.5000 M NaOH. What is the final pH? The Ka of acetic acid is 1.770× 10- 5.

Calculate the pH of a buffer that contains 0.270 M hydrofluoric acid (HF) and 0.180 M cesium fluoride (CsF). The Ka of hydrofluoric acid is 6.80 × 10- 4.

Of the substances below, will decrease the solubility of Pb(OH) 2 in a saturated solution.

Which of the following could be added to a solution of acetic acid to prepare a buffer? sodium acetate sodium hydroxide nitric acid hydrofluoric acid

A solution containing which one of the following pairs of substances will be a buffer solution?

Calculate the pH of a solution that is 0.210 M in nitrous acid (HNO2) and 0.290 M in potassium nitrite (KNO2) . The acid dissociation constant of nitrous acid is 4.50 × 10- 4.

In which of the following aqueous solutions would you expect AgBr to have the lowest solubility?

A 25.0 mL sample of 0.723 M HClO4 is titrated with a 0.273 M KOH solution. The H3O+ concentration after the addition of 10.0 mL of KOH is M.

What is the molar solubility of barium fluoride ( BaF2 ) in water? The solubility- product constant for BaF2 is 1.7 × 10- 6 at 25°C.

For which salt should the aqueous solubility be most sensitive to pH?

The Ka of acetic acid is 1.76 × 10- 5. The pH of a buffer prepared by combining 50.0 mL of 1.00 M potassium acetate and 50.0 mL of 1.00 M acetic acid is _ .

Suppose you have just added 100.0 ml of a solution containing 0.5000 moles of acetic acid per liter to 400.0 ml of 0.5000 M NaOH. What is the final pH? The Ka of acetic acid is 1.770× 10- 5.

200.0 ml of a solution containing 0.5000 moles of acetic acid per liter is added to 200.0 ml of 0.5000 M NaOH. What is the final pH? The Ka of acetic acid is 1.770 × 10- 5.

Calculate the percent ionization of formic acid (HCO2H) in a solution that is 0.219 M in formic acid. The Ka of formic acid is 1.77 × 10- 4.

Calculate the pH of a buffer solution that contains 0.820 grams of sodium acetate and 0.01 moles of acetic acid in 100 ml of water. The Ka of acetic acid is 1.77 × 10- 5.

Which of the following could be added to a solution of sodium acetate to produce a buffer? acetic acid hydrochloric acid potassium acetate sodium chloride

Which below best describe(s) the behavior of an amphoteric hydroxide in water?

What is the pH of a buffer solution that is 0.255 M in hypochlorous acid (HClO) and 0.333 M in sodium hypochlorite? The Ka of hypochlorous acid is 3.81 × 10- 8.

Calculate the percent ionization of formic acid (HCO₂H) in a solution that is 0.311 M in formic acid and 0.189 M in sodium formate (NaHCO₂) . The K_aof formic acid is 1.77 ×10^-⁴.

Suppose you have just added 200.0 ml of a solution containing 0.5000 moles of acetic acid per liter to 100.0 ml of 0.5000 M NaOH. What is the final pH? The Ka of acetic acid is 1.770× 10^-⁵.

Calculate the pH of a buffer that contains 0.270 M hydrofluoric acid (HF) and 0.180 M cesium fluoride (CsF). The Ka of hydrofluoric acid is 6.80 × 10^-⁴.

Of the substances below, will decrease the solubility of Pb(OH) ₂in a saturated solution.

Calculate the pH of a solution that is 0.210 M in nitrous acid (HNO₂) and 0.290 M in potassium nitrite (KNO₂) . The acid dissociation constant of nitrous acid is 4.50 × 10^-⁴.

A 25.0 mL sample of 0.723 M HClO₄is titrated with a 0.273 M KOH solution. The H₃O⁺ concentration after the addition of 10.0 mL of KOH is M.

What is the molar solubility of barium fluoride ( BaF₂) in water? The solubility- product constant for BaF₂is 1.7 × 10^-⁶at 25°C.

The K_aof acetic acid is 1.76 × 10^-⁵. The pH of a buffer prepared by combining 50.0 mL of 1.00 M potassium acetate and 50.0 mL of 1.00 M acetic acid is _ .

Suppose you have just added 100.0 ml of a solution containing 0.5000 moles of acetic acid per liter to 400.0 ml of 0.5000 M NaOH. What is the final pH? The Ka of acetic acid is 1.770× 10^-⁵.

200.0 ml of a solution containing 0.5000 moles of acetic acid per liter is added to 200.0 ml of 0.5000 M NaOH. What is the final pH? The Ka of acetic acid is 1.770 × 10^-⁵.

Calculate the percent ionization of formic acid (HCO₂H) in a solution that is 0.219 M in formic acid. The K_aof formic acid is 1.77 × 10^-⁴.

Calculate the pH of a buffer solution that contains 0.820 grams of sodium acetate and 0.01 moles of acetic acid in 100 ml of water. The Ka of acetic acid is 1.77 × 10^-⁵.

What is the pH of a buffer solution that is 0.255 M in hypochlorous acid (HClO) and 0.333 M in sodium hypochlorite? The K_aof hypochlorous acid is 3.81 × 10^-⁸.