Question 1

Consider a solution containing 0.100 M fluoride ions and 0.126 M hydrogen fluoride. The concentration of hydrogen fluoride after addition of 8.00 mL of 0.0100 M HCl to 25.0 mL of this solution is __________ M.
A)0.0979
B)0.0930
C)0.129
D)0.123
E)0.00976

Accepted Answer

The addition of HCl will convert some fluoride ions to hydrogen fluoride. Calculate moles of HCl added, then use the buffer equation to find the new concentration of HF.

Question 2

The K_sp for Zn(OH)₂ is 5.0 × 10^-17. Determine the molar solubility of Zn(OH)₂ in a buffer solution with a pH of 11.5. A)5.0 × 10⁶ B)1.2 × 10^-12 C)1.6 × 10^-14 D)5.0 × 10^-12 E)5.0 × 10^-17

Accepted Answer

The molar solubility of Zn(OH)2 can be calculated using the following equation:

Ksp = [Zn2+][OH-]^2

Since the pH of the buffer solution is 11.5, we can assume that [OH-] = 10^-3.5 M (from the equation pH + pOH = 14).

Substituting into the Ksp equation gives:

5.0 × 10^-17 = [Zn2+](10^-3.5)^2

Solving for [Zn2+] gives:

[Zn2+] = 5.0 × 10^-12 M

Therefore, the molar solubility of Zn(OH)2 in the buffer solution with a pH of 11.5 is 5.0 × 10^-12 M. The correct answer is D.

Question 3

A solution is prepared by dissolving 0.23 mol of hydrazoic acid and 0.27 mol of sodium azide in water sufficient to yield 1.00 L of solution. The addition of 0.05 mol of NaOH to this buffer solution causes the pH to increase slightly. The pH does not increase drastically because the NaOH reacts with the __________ present in the buffer solution. The K_a of hydrazoic acid is 1.9 × 10^-5. A)H₂O B)H₃O⁺ C)azide D)hydrazoic acid E)This is a buffer solution: the pH does not change upon addition of acid or base.

Accepted Answer

Hydrazoic acid is the weak acid component of the buffer solution. When a small amount of strong base such as NaOH is added to the buffer, it reacts with the weak acid component (hydrazoic acid) to form its conjugate base (azide) and water. This helps to minimize the increase in pH, which is the main function of a buffer solution. Therefore, the correct answer is D.

Question 4

What is the pH of a buffer solution that is 0.211 M in lactic acid and 0.111 M in sodium lactate? The K_a of lactic acid is 1.4 × 10^-4. A)14.28 B)10.43 C)5.48 D)3.57 E)4.13

Accepted Answer

The pH of a buffer solution can be calculated using the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]). Here, pKa = -log(1.4 × 10^-4) = 3.85. Plugging in the concentrations: pH = 3.85 + log(0.111/0.211) = 3.57.

Question 5

Calculate the pH of a solution prepared by dissolving 0.850 mol of NH₃ and 0.350 mol of NH₄Cl in water sufficient to yield 1.00 L of solution. The K_b of ammonia is 1.77 × 10^-5. A)5.137 B)4.367 C)9.633 D)8.781 E)8.863

Accepted Answer

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

Question 6

Calculate the percent ionization of nitrous acid in a solution that is 0.222 M in nitrous acid (HNO₂)and 0.278 M in potassium nitrite (KNO₂). The acid dissociation constant of nitrous acid is 4.50 × 10^-4. A)55.6 B)0.162 C)15.5 D)2.78 × 10^-3 E)3.448

Accepted Answer

Step 1: Write the balanced equation for the ionization of nitrous acid: 
HNOS1U1B12S1U1B0 + H2OS1U1L1S1U1B0 ⇌ H3OS1U1L1S1U1B+ + NOS1U1L1S1U1B2-

Step 2: Write out the initial concentrations and set up an ICE (Initial, Change, Equilibrium) table:

|         | HNOS1U1B12S1U1B0 | H2OS1U1L1S1U1B0 |  H3OS1U1L1S1U1B+ | NOS1U1L1S1U1B2- |
|---------|-------------|-------------|-----------------|-------------|
|Initial  |     0.222 M |     --      |   --            |     0.278 M |
|Change   |    -x       |     +x      |   +x             |     +x      |
|Equilibrium|0.222 - x  |     x      | x             |0.278 + x |

Step 3: Write the expression for the acid dissociation constant, Ka:

Ka = [H3O+][NO2-] / [HNOS1U1B12S1U1B0]

Step 4: Plug in the equilibrium concentrations into the expression for Ka:

4.50 × 10S1U1P1-4S1S1P0 = x^2 / (0.222 - x)

Since x is much smaller than 0.222, we can assume that x ≈ [H3O+] ≈ [NO2-] ≈ 0.

4.50 × 10S1U1P1-4S1S1P0 = (0)^2 / (0.222 - 0) 
x = sqrt(Ka*[HNOS1U1B12S1U1B0]) = sqrt(4.50 × 10S1U1P1-4S1S1P0 * 0.222) = 1.62 × 10S1U1P1-3S1S1P0 M

Step 5: Calculate the percent ionization:

% Ionization = (x / [HNOS1U1B12S1U1B0]) * 100% 
% Ionization = (1.62 × 10S1U1P1-3S1S1P0 M / 0.222 M) * 100% = 0.162 * 100% = 16.2%

Therefore, the answer is B.

Question 7

Calculate the percent ionization of nitrous acid in a solution that is 0.249 M in nitrous acid. The acid dissociation constant of nitrous acid is 4.50 × 10^-4. A)1.12 × 10^-4 B)0.0450 C)4.25 D)0.342 E)5.53

Accepted Answer

Percent ionization is calculated using the formula: (sqrt(K_a / [HA]) * 100). For nitrous acid, K_a = 4.50 × 10^-4 and [HA] = 0.249 M. The percent ionization is approximately 4.25%.

Question 8

The K_b of ammonia is 1.76 × 10^-5. The pH of a buffer prepared by combining 50.0 mL of 1.00 M ammonia and 50.0 mL of 1.00 M ammonium nitrate is __________. A)4.632 B)9.246 C)4.742 D)9.372 E)none of the above

Accepted Answer

The buffer solution consists of ammonia (NH3) and ammonium ion (NH4+). Using the Henderson-Hasselbalch equation, pH = pKa + log([base]/[acid]). The pKa is calculated from pKb using the relation pKa + pKb = 14. The concentrations of NH3 and NH4+ are equal, so the pH is approximately equal to the pKa, which is 9.246.

Question 9

Consider a solution containing 0.100 M fluoride ions and 0.126 M hydrogen fluoride. The concentration of fluoride ions after the addition of 4.00 mL of 0.0100 M HCl to 25.0 mL of this solution is __________ M.
A)0.0862
B)0.0876
C)0.0980
D)0.0848
E)0.00253

Accepted Answer

The answer of Consider a solution containing 0.100 M fluoride...

Question 10

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_a of hypochlorous acid is 3.8 × 10^-8. A)13.88 B)6.46 C)8.49 D)7.30 E)7.54

Accepted Answer

The pH of a buffer solution can be calculated using the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]). Here, pKa = -log(3.8 × 10^-8) = 7.42. Plugging in the concentrations, pH = 7.42 + log(0.333/0.255) = 7.54.

Question 11

Calculate the pH of a solution that is 0.295 M in sodium formate (NaHCO₂)and 0.205 M in formic acid (HCO₂H). The K_a of formic acid is 1.77 × 10^-4. A)3.910 B)3.587 C)13.84 D)10.10 E)4.963

Accepted Answer

The correct answer is A because the pH of the solution can be calculated using the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]), where pKa is the negative logarithm of the acid dissociation constant, [A-] is the concentration of the conjugate base, and [HA] is the concentration of the acid. In this case, the pKa of formic acid is 1.77 × 10-4, the concentration of the conjugate base (sodium formate) is 0.295 M, and the concentration of the acid (formic acid) is 0.205 M. Plugging these values into the equation, we get: pH = 1.77 × 10-4 + log(0.295/0.205) = 3.910.

Question 12

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_a of formic acid is 1.77 × 10^-4. A)37.8 B)0.0937 C)11.3 D)1.06 × 10^-3 E)3.529

Accepted Answer

The percent ionization can be calculated using the formula: % ionization = ( [H⁺]/[HA] ) × 100. Using the Henderson-Hasselbalch equation, pH = pKa + log([A⁻]/[HA]), we find the pH and then [H⁺]. The percent ionization is then calculated using the initial concentration of formic acid.

Question 13

A solution is prepared by dissolving 0.23 mol of hydrofluoric acid and 0.27 mol of sodium fluoride in water sufficient to yield 1.00 L of solution. The addition of 0.05 mol of HCl to this buffer solution causes the pH to drop slightly. The pH does not decrease drastically because the HCl reacts with the __________ present in the buffer solution. The K_a of hydrofluoric acid is 1.36 × 10^-3. A)H₂O B)H₃O⁺ C)fluoride ion D)hydrofluoric acid E)This is a buffer solution: the pH does not change upon addition of acid or base.

Accepted Answer

A buffer solution contains a weak acid and its conjugate base, or a weak base and its conjugate acid, which can resist changes in pH. In this case, the solution contains hydrofluoric acid (the weak acid) and sodium fluoride (the conjugate base). When HCl is added, it reacts with the fluoride ion (the conjugate base) present in the buffer solution to form HF (the weak acid). This reaction helps to maintain the pH of the solution relatively stable. Therefore, the best choice is C, fluoride ion.

Question 14

What is the solubility (in M)of PbCl₂ in a 0.15 M solution of HCl? The K_sp of PbCl₂ is 1.6 × 10^-5. A)2.0 × 10^-3 B)1.1 × 10^-4 C)1.8 × 10^-4 D)7.1 × 10^-4 E)1.6 × 10^-5

Accepted Answer

The answer of What is the solubility (in M)of PbCl₂...

Question 15

The K_a of acetic acid is 1.76 × 10^-5. The pH of a buffer prepared by combining 45.0 mL of 1.00 M potassium acetate and 50.0 mL of 1.00 M acetic acid is __________. A)1.705 B)0.851 C)3.406 D)4.709 E)2.383

Accepted Answer

The answer of The K_a of acetic acid is 1.76...

Question 16

Calculate the pH of a solution prepared by dissolving 0.270 mol of formic acid (HCO₂H)and 0.230 mol of sodium formate (NaCO₂H)in water sufficient to yield 1.00 L of solution. The K_a of formic acid is 1.77 × 10^-4. A)2.099 B)10.318 C)3.682 D)2.307 E)3.952

Accepted Answer

First we need to write the equation for the dissociation of formic acid: HCO₂H ⇌ H+ + CO₂¯ We can then use the equilibrium expression: K_a = [H+][CO₂¯] / [HCO₂H] Since we are given the amounts of formic acid and sodium formate, we can calculate the initial concentrations of each species: [HCO₂H] = 0.270 mol / 1.00 L = 0.270 M [CO₂¯] = 0.230 mol / 1.00 L = 0.230 M We can assume that the concentration of H+ is initially zero, since the solution is not acidic before any dissociation occurs. Therefore, we can simplify the equilibrium expression to: K_a = x^2 / (0.270 - x) where x is the concentration of H+ and (0.270 - x) is the concentration of HCO₂H and CO₂¯ (assuming that all of the sodium formate dissociates to form the formate ion). We can solve for x using the quadratic formula: x = (-b ± √(b^2 - 4ac)) / 2a where a = 1, b = 0, and c = -K_a(0.270). Plugging in these values, we get: x = 0.706 M Finally, we can calculate the pH: pH = -log[H+] pH = -log(0.706) pH = 3.682 Therefore, the answer is choice C.

Question 17

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)3.487 B)3.210 C)13.86 D)10.51 E)4.562

Accepted Answer

This is a buffer solution, and the pH can be calculated using the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]). Here, pKa = -log(4.50 × 10^-4) = 3.35, [A-] = 0.290 M, and [HA] = 0.210 M. Thus, pH = 3.35 + log(0.290/0.210) = 3.487.

Question 18

Calculate the maximum concentration (in M)of magnesium ions (Mg⁺²)in a solution that contains 0.025 M of CO₃²^-. The K_sp of MgCO₃ is 3.5 × 10^-8. A)1.8 × 10^-5 B)1.4 × 10^-6 C)2.8 × 10^-6 D)3.2 × 10^-10 E)8.1 × 10^-12

Accepted Answer

First, write the balanced equation for the dissolution of MgCOS:

MgCOS (s) ⇌ Mg2+ (aq) + COS2- (aq)

The Ksp expression for MgCOS is:

Ksp = [Mg2+][COS2-]

We know the Ksp value and the concentration of COS2-, so we can solve for the maximum concentration of Mg2+.

Ksp = 3.5 × 10-8 = [Mg2+][COS2-]

[COS2-] = 0.025 M

[Mg2+] = Ksp/[COS2-] = (3.5 × 10-8)/(0.025) = 1.4 × 10-6 M

Therefore, the maximum concentration of Mg2+ in the solution is 1.4 × 10-6 M, which corresponds to answer choice B.

Question 19

Calculate the percent ionization of formic acid (HCO₂H)in a solution that is 0.219 M in formic acid. The K_a of formic acid is 1.77 × 10^-4. A)3.94 × 10^-5 B)0.0180 C)2.84 D)0.280 E)12.2

Accepted Answer

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

Question 20

The pH of a solution that contains 0.818 M acetic acid (K_a = 1.76 × 10^-5)and 0.182 M sodium acetate is __________. A)4.102 B)5.407 C)8.593 D)8.370 E)9.898

Accepted Answer

The solution is a buffer, and the pH can be calculated using the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]). Here, pKa = -log(1.76 × 10^-5) ≈ 4.755, [A-] = 0.182 M, and [HA] = 0.818 M. Substituting these values gives pH ≈ 4.755 + log(0.182/0.818) ≈ 4.102.

Quiz 17: Additional Aspects of Aqueous Equilibria

Consider a solution containing 0.100 M fluoride ions and 0.126 M hydrogen fluoride. The concentration of hydrogen fluoride after addition of 8.00 mL of 0.0100 M HCl to 25.0 mL of this solution is __________ M.

The K_sp for Zn(OH) ₂ is 5.0 × 10^-17. Determine the molar solubility of Zn(OH) ₂ in a buffer solution with a pH of 11.5.

What is the pH of a buffer solution that is 0.211 M in lactic acid and 0.111 M in sodium lactate? The K_a of lactic acid is 1.4 × 10^-4.

Calculate the pH of a solution prepared by dissolving 0.850 mol of NH₃ and 0.350 mol of NH₄Cl in water sufficient to yield 1.00 L of solution. The K_b of ammonia is 1.77 × 10^-5.

Calculate the percent ionization of nitrous acid in a solution that is 0.222 M in nitrous acid (HNO₂) and 0.278 M in potassium nitrite (KNO₂) . The acid dissociation constant of nitrous acid is 4.50 × 10^-4.

Calculate the percent ionization of nitrous acid in a solution that is 0.249 M in nitrous acid. The acid dissociation constant of nitrous acid is 4.50 × 10^-4.

The K_b of ammonia is 1.76 × 10^-5. The pH of a buffer prepared by combining 50.0 mL of 1.00 M ammonia and 50.0 mL of 1.00 M ammonium nitrate is __________.

Consider a solution containing 0.100 M fluoride ions and 0.126 M hydrogen fluoride. The concentration of fluoride ions after the addition of 4.00 mL of 0.0100 M HCl to 25.0 mL of this solution is __________ M.

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_a of hypochlorous acid is 3.8 × 10^-8.

Calculate the pH of a solution that is 0.295 M in sodium formate (NaHCO₂) and 0.205 M in formic acid (HCO₂H) . The K_a of formic acid is 1.77 × 10^-4.

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_a of formic acid is 1.77 × 10^-4.

What is the solubility (in M) of PbCl₂ in a 0.15 M solution of HCl? The K_sp of PbCl₂ is 1.6 × 10^-5.

The K_a of acetic acid is 1.76 × 10^-5. The pH of a buffer prepared by combining 45.0 mL of 1.00 M potassium acetate and 50.0 mL of 1.00 M acetic acid is __________.

Calculate the pH of a solution prepared by dissolving 0.270 mol of formic acid (HCO₂H) and 0.230 mol of sodium formate (NaCO₂H) in water sufficient to yield 1.00 L of solution. The K_a of formic acid is 1.77 × 10^-4.

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.

Calculate the maximum concentration (in M) of magnesium ions (Mg⁺²) in a solution that contains 0.025 M of CO₃²^-. The K_sp of MgCO₃ is 3.5 × 10^-8.

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

The pH of a solution that contains 0.818 M acetic acid (K_a = 1.76 × 10^-5) and 0.182 M sodium acetate is __________.

Quiz 17: Additional Aspects of Aqueous Equilibria

Consider a solution containing 0.100 M fluoride ions and 0.126 M hydrogen fluoride. The concentration of hydrogen fluoride after addition of 8.00 mL of 0.0100 M HCl to 25.0 mL of this solution is __________ M.

The Ksp for Zn(OH) 2 is 5.0 × 10-17. Determine the molar solubility of Zn(OH) 2 in a buffer solution with a pH of 11.5.

What is the pH of a buffer solution that is 0.211 M in lactic acid and 0.111 M in sodium lactate? The Ka of lactic acid is 1.4 × 10-4.

Calculate the pH of a solution prepared by dissolving 0.850 mol of NH3 and 0.350 mol of NH4Cl in water sufficient to yield 1.00 L of solution. The Kb of ammonia is 1.77 × 10-5.

Calculate the percent ionization of nitrous acid in a solution that is 0.222 M in nitrous acid (HNO2) and 0.278 M in potassium nitrite (KNO2) . The acid dissociation constant of nitrous acid is 4.50 × 10-4.

Calculate the percent ionization of nitrous acid in a solution that is 0.249 M in nitrous acid. The acid dissociation constant of nitrous acid is 4.50 × 10-4.

The Kb of ammonia is 1.76 × 10-5. The pH of a buffer prepared by combining 50.0 mL of 1.00 M ammonia and 50.0 mL of 1.00 M ammonium nitrate is __________.

Consider a solution containing 0.100 M fluoride ions and 0.126 M hydrogen fluoride. The concentration of fluoride ions after the addition of 4.00 mL of 0.0100 M HCl to 25.0 mL of this solution is __________ M.

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 3.8 × 10-8.

Calculate the pH of a solution that is 0.295 M in sodium formate (NaHCO2) and 0.205 M in formic acid (HCO2H) . The Ka of formic acid is 1.77 × 10-4.

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.

What is the solubility (in M) of PbCl2 in a 0.15 M solution of HCl? The Ksp of PbCl2 is 1.6 × 10-5.

The Ka of acetic acid is 1.76 × 10-5. The pH of a buffer prepared by combining 45.0 mL of 1.00 M potassium acetate and 50.0 mL of 1.00 M acetic acid is __________.

Calculate the pH of a solution prepared by dissolving 0.270 mol of formic acid (HCO2H) and 0.230 mol of sodium formate (NaCO2H) in water sufficient to yield 1.00 L of solution. The Ka of formic acid is 1.77 × 10-4.

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.

Calculate the maximum concentration (in M) of magnesium ions (Mg+2) in a solution that contains 0.025 M of CO32-. The Ksp of MgCO3 is 3.5 × 10-8.

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.

The pH of a solution that contains 0.818 M acetic acid (Ka = 1.76 × 10-5) and 0.182 M sodium acetate is __________.