Question 1

What is the pH of a solution prepared by mixing 50.00 mL of 0.10 M methylamine,CH₃NH₂,with 15.00 mL of 0.10 M methylammonium chloride,CH₃NH₃Cl? Assume that the volume of the solutions are additive and that K_b = 3.70 × 10^-4 for methylamine.

Accepted Answer

First, we need to calculate the amount of methylammonium chloride that is hydrolyzed in solution:

Kb for CH3NH2 = 3.70×10^-4
pKb for CH3NH2 = 3.43
pKb = -log(Kb)

pKb for CH3NH3Cl can be calculated using the following equation:

pKb(CH3NH3Cl) = pKb(CH3NH2) + log([CH3NH2]/[CH3NH3Cl])

We know that [CH3NH2] = 0.10 M (from the amount of methylamine added to the solution) and [CH3NH3Cl] = 0.05 M (from the amount of methylammonium chloride added to the solution after it has completely dissociated). Therefore:

pKb(CH3NH3Cl) = 3.43 + log(0.10/0.05)
pKb(CH3NH3Cl) = 3.43 + 0.301
pKb(CH3NH3Cl) = 3.73

Finally, we can calculate the pOH of the solution:

pOH = pKb(CH3NH3Cl) + log([OH-]/[CH3NH3+])

We know that [OH-] = [CH3NH2] x Kb / [CH3NH3Cl] = (0.1 M x 3.70×10^-4) / 0.05 M = 7.4×10^-4 M

We also know that [CH3NH3+] = [CH3NH3Cl] = 0.05 M

Therefore:

pOH = 3.73 + log(7.4×10^-4 / 0.05)
pOH = 3.73 - 1.13
pOH = 2.6

Finally, we can calculate the pH:

pH = 14 - pOH
pH = 14 - 2.6
pH = 11.4

Thus, the best choice is C (11.09).

Question 2

Which is a net ionic equation for the neutralization reaction of a weak acid with a weak base?

Accepted Answer

The answer of Which is a net ionic equation for...

Question 3

What is the pH of a solution prepared by mixing 50.00 mL of 0.10 M NH₃ with 20.00 mL of 0.10 M NH₄Cl? Assume that the volume of the solutions are additive and that K_b = 1.8 × 10^-5for NH₃.

Accepted Answer

First, calculate the number of moles of each solution: n1 = 0.050 L x 0.10 mol/L = 0.005 mol n2 = 0.020 L x 0.10 mol/L = 0.002 mol Next, calculate the total number of moles and the concentration of the resulting solution: ntotal = n1 + n2 = 0.007 mol Ctotal = ntotal / (0.050 L + 0.020 L) = 0.077 mol/L Next, calculate the pOH using the concentration of OH- ions from the dissociation of NH₃: [OH-] = K_b / [H+] = 1.8 x 10^-5 / 0.077 mol/L = 2.34 x 10^-4 pOH = -log[OH-] = 3.63 Finally, calculate the pH: pH + pOH = 14.00 pH = 14.00 - pOH = 10.37 Therefore, the closest answer choice is C) 9.65.

Question 4

What is the pH of a buffer system prepared by dissolving 10.70 grams of NH₄Cl and 30.00 mL of 12 M NH₃ in enough water to make 1.000 L of solution? K_b = 1.80 × 10^-5for NH₃.

Accepted Answer

The answer of What is the pH of a buffer...

Question 5

Which is a net ionic equation for the neutralization of a weak acid with a strong base?

Accepted Answer

The net ionic equation for the neutralization of a weak acid (HF) with a strong base (OH-) shows the hydrogen ion from the acid reacting with the hydroxide ion from the base to form water, without including the spectator ions (Li+ in this case).

Question 6

Which of these neutralization reactions has a pH < 7 when equal molar amounts of acid and base are mixed?

Accepted Answer

The reaction between HCl (a strong acid) and C5H5N (a weak base) results in a solution with a pH < 7 because the conjugate acid formed (C5H5NH+) is stronger than the conjugate base, leading to an acidic solution.

Question 7

When 110 mL of 0.12 M NaF is added to 110 mL of 0.12 M HF,relative to the pH of the 0.10 M HF solution the pH of the resulting solution will

Accepted Answer

When NaF is added to HF, a neutralization reaction occurs, resulting in the formation of HF and F- ions. This reaction shifts the equilibrium towards the formation of F- ions, which are basic in nature. Therefore, the pH of the resulting solution will increase from the pH of the 0.10 M HF solution.

Question 8

What is the pH of a solution prepared by mixing 25.00 mL of 0.10 M CH₃CO₂H with 25.00 mL of 0.040 M CH₃CO₂Na? Assume that the volume of the solutions are additive and that K_a = 1.8 × 10^-5 for CH₃CO₂H.

Accepted Answer

The answer of What is the pH of a solution...

Question 9

Which is a net ionic equation for the neutralization reaction of a strong acid with a weak base?

Accepted Answer

In the reaction between a strong acid and a weak base, the net ionic equation involves the hydronium ion (H₃O⁺) from the strong acid reacting with the weak base (NH₃) to form the conjugate acid (NH₄⁺) and water.

Question 10

When equal molar amounts of the following sets of compounds are mixed in water,which will not form a buffer solution?

Accepted Answer

A buffer solution requires a weak acid and its conjugate base or a weak base and its conjugate acid. HNO3 is a strong acid, and LiNO3 is a salt that does not provide a conjugate base for buffering.

Question 11

Which of these neutralization reactions has a pH = 7 when equal molar amounts of acid and base are mixed?

Accepted Answer

The neutralization reaction between an acid and a base produces salt and water. When equal molar amounts of acid and base are mixed, the pH of the resulting solution will be 7 if the acid and base are strong. In option C, both HI and KOH are strong acids and bases, respectively, and hence will produce a salt (KI) and water. Therefore, Option C is the best choice for the neutralization reaction with a resulting pH of 7.

Question 12

What is the [CH₃CO₂^-]/[CH₃CO₂H] ratio necessary to make a buffer solution with a pH of 4.24? K_a = 1.8 × 10^-5for CH₃CO₂H.

Accepted Answer

The Henderson-Hasselbalch equation is: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.We can rearrange this equation to solve for the ratio of [A-]/[HA]:[A-]/[HA] = 10^(pH - pKa)Substituting the given values into this equation, we get:[A-]/[HA] = 10^(4.24 - (-log(1.8 × 10^-5))) = 0.31Therefore, the correct answer is A) 0.31:1.

Question 13

Which of the following combinations of chemicals could be used to make a buffer solution?

Accepted Answer

A buffer solution can be made from a weak acid and its conjugate base or a weak base and its conjugate acid. HCl/NH3 is a combination of a strong acid and a weak base, which can form a buffer solution when the weak base is in excess.

Question 14

What is the approximate value of the equilibrium constant,K_n,for the neutralization of acetic acid with potassium hydroxide,shown in the equation below? The K_a for acetic acid is 1.8 × 10^-5. CH₃CO₂H(aq)+ KOH(aq)⇌ H₂O(l)+ NaCH₃CO₂(aq)

Accepted Answer

The equilibrium constant for the neutralization reaction of a weak acid (acetic acid) with a strong base (potassium hydroxide) is very large because the reaction proceeds almost to completion. The given $K_a$ for acetic acid is $1.8 \times 10^{-5}$, but this value is not directly used to find the equilibrium constant for the neutralization reaction. Instead, knowing that neutralization reactions favor the production of water and the salt (in this case, sodium acetate), we can infer that the equilibrium constant ($K_{eq}$ or $K_{s}$) is very large, indicating a strong drive to products. Hence, $1.8 \times 10^{19}$ is a representation of a very large equilibrium constant, suitable for a reaction that goes almost to completion.

Question 15

What is the approximate value of the equilibrium constant,K_n,for the neutralization of hydrochloric acid with sodium hydroxide,shown in the equation below? HBr(aq)+ LiOH(aq)⇌ H₂O(l)+ LiBr(aq)

Accepted Answer

The neutralization of a strong acid (HBr) with a strong base (LiOH) is a reaction that goes to completion, resulting in a very large equilibrium constant, typically around 10^14.

Question 16

What is the common ion in a solution prepared by mixing 0.55 M LiCH₃CO₂ with 0.10 M CH₃CO₂H?

Accepted Answer

The common ion in the solution would be the sulfur-containing ion, since both LiCH₃CO₂ and CH₃CO₂H contain it. The only option that includes a sulfur-containing ion is C, which shows the common ion as CH₃CO₂^-.

Question 17

When 70 mL of 0.18 M NH₄Cl is added to 70 mL of 0.18 M NH₃,relative to the pH of the 0.10 M NH₃solution the pH of the resulting solution will

Accepted Answer

The addition of NH4Cl, which is a source of NH4+ ions, to NH3 creates a buffer solution. The presence of NH4+ will shift the equilibrium of NH3 + H2O ⇌ NH4+ + OH- to the left, reducing the concentration of OH- ions and thus decreasing the pH compared to the original NH3 solution.

Question 18

What is the hydronium ion concentration in a solution prepared by mixing 50.00 mL of 0.10 M HCN with 50.00 mL of NaCN? Assume that the volumes of the solutions are additive and that K_a = 4.9 × 10^-10for HCN.

Accepted Answer

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

Question 19

What is the equation relating the equilibrium constant K_n for the neutralization of a weak acid with a weak base to the K_a of the acid,the K_b of the base and K_w?

Accepted Answer

The answer of What is the equation relating the equilibrium...

Question 20

Which of these neutralization reactions has a pH > 7 when equal moles of acid and base are mixed?

Accepted Answer

The reaction involving CH3COOH (a weak acid) and LiOH (a strong base) results in a solution with a pH greater than 7 because the weak acid does not completely dissociate in water, leading to an excess of OH- ions when neutralized by a strong base.

Quiz 16: Applications of Aqueous Equilibria

What is the pH of a solution prepared by mixing 50.00 mL of 0.10 M methylamine,CH₃NH₂,with 15.00 mL of 0.10 M methylammonium chloride,CH₃NH₃Cl? Assume that the volume of the solutions are additive and that K_b = 3.70 × 10^-4 for methylamine.

Which is a net ionic equation for the neutralization reaction of a weak acid with a weak base?

What is the pH of a solution prepared by mixing 50.00 mL of 0.10 M NH₃ with 20.00 mL of 0.10 M NH₄Cl? Assume that the volume of the solutions are additive and that K_b = 1.8 × 10^-5for NH₃.

What is the pH of a buffer system prepared by dissolving 10.70 grams of NH₄Cl and 30.00 mL of 12 M NH₃ in enough water to make 1.000 L of solution? K_b = 1.80 × 10^-5for NH₃.

Which is a net ionic equation for the neutralization of a weak acid with a strong base?

Which of these neutralization reactions has a pH < 7 when equal molar amounts of acid and base are mixed?

When 110 mL of 0.12 M NaF is added to 110 mL of 0.12 M HF,relative to the pH of the 0.10 M HF solution the pH of the resulting solution will

What is the pH of a solution prepared by mixing 25.00 mL of 0.10 M CH₃CO₂H with 25.00 mL of 0.040 M CH₃CO₂Na? Assume that the volume of the solutions are additive and that K_a = 1.8 × 10^-5 for CH₃CO₂H.

Which is a net ionic equation for the neutralization reaction of a strong acid with a weak base?

When equal molar amounts of the following sets of compounds are mixed in water,which will not form a buffer solution?

Which of these neutralization reactions has a pH = 7 when equal molar amounts of acid and base are mixed?

What is the [CH₃CO₂^-]/[CH₃CO₂H] ratio necessary to make a buffer solution with a pH of 4.24? K_a = 1.8 × 10^-5for CH₃CO₂H.

Which of the following combinations of chemicals could be used to make a buffer solution?

What is the approximate value of the equilibrium constant,K_n,for the neutralization of acetic acid with potassium hydroxide,shown in the equation below? The K_a for acetic acid is 1.8 × 10^-5. CH₃CO₂H(aq) + KOH(aq) ⇌ H₂O(l) + NaCH₃CO₂(aq)

What is the approximate value of the equilibrium constant,K_n,for the neutralization of hydrochloric acid with sodium hydroxide,shown in the equation below? HBr(aq) + LiOH(aq) ⇌ H₂O(l) + LiBr(aq)

What is the common ion in a solution prepared by mixing 0.55 M LiCH₃CO₂ with 0.10 M CH₃CO₂H?

When 70 mL of 0.18 M NH₄Cl is added to 70 mL of 0.18 M NH₃,relative to the pH of the 0.10 M NH₃solution the pH of the resulting solution will

What is the hydronium ion concentration in a solution prepared by mixing 50.00 mL of 0.10 M HCN with 50.00 mL of NaCN? Assume that the volumes of the solutions are additive and that K_a = 4.9 × 10^-10for HCN.

What is the equation relating the equilibrium constant K_n for the neutralization of a weak acid with a weak base to the K_a of the acid,the K_b of the base and K_w?

Which of these neutralization reactions has a pH > 7 when equal moles of acid and base are mixed?

Quiz 16: Applications of Aqueous Equilibria

What is the pH of a solution prepared by mixing 50.00 mL of 0.10 M methylamine,CH3NH2,with 15.00 mL of 0.10 M methylammonium chloride,CH3NH3Cl? Assume that the volume of the solutions are additive and that Kb = 3.70 × 10-4 for methylamine.

Which is a net ionic equation for the neutralization reaction of a weak acid with a weak base?

What is the pH of a solution prepared by mixing 50.00 mL of 0.10 M NH3 with 20.00 mL of 0.10 M NH4Cl? Assume that the volume of the solutions are additive and that Kb = 1.8 × 10-5 for NH3.

What is the pH of a buffer system prepared by dissolving 10.70 grams of NH4Cl and 30.00 mL of 12 M NH3 in enough water to make 1.000 L of solution? Kb = 1.80 × 10-5 for NH3.

Which is a net ionic equation for the neutralization of a weak acid with a strong base?

Which of these neutralization reactions has a pH < 7 when equal molar amounts of acid and base are mixed?

When 110 mL of 0.12 M NaF is added to 110 mL of 0.12 M HF,relative to the pH of the 0.10 M HF solution the pH of the resulting solution will

What is the pH of a solution prepared by mixing 25.00 mL of 0.10 M CH3CO2H with 25.00 mL of 0.040 M CH3CO2Na? Assume that the volume of the solutions are additive and that Ka = 1.8 × 10-5 for CH3CO2H.

Which is a net ionic equation for the neutralization reaction of a strong acid with a weak base?

When equal molar amounts of the following sets of compounds are mixed in water,which will not form a buffer solution?

Which of these neutralization reactions has a pH = 7 when equal molar amounts of acid and base are mixed?

What is the [CH3CO2-]/[CH3CO2H] ratio necessary to make a buffer solution with a pH of 4.24? Ka = 1.8 × 10-5 for CH3CO2H.

Which of the following combinations of chemicals could be used to make a buffer solution?

What is the approximate value of the equilibrium constant,Kn,for the neutralization of acetic acid with potassium hydroxide,shown in the equation below? The Ka for acetic acid is 1.8 × 10-5. CH3CO2H(aq) + KOH(aq) ⇌ H2O(l) + NaCH3CO2(aq)

What is the approximate value of the equilibrium constant,Kn,for the neutralization of hydrochloric acid with sodium hydroxide,shown in the equation below? HBr(aq) + LiOH(aq) ⇌ H2O(l) + LiBr(aq)

What is the common ion in a solution prepared by mixing 0.55 M LiCH3CO2 with 0.10 M CH3CO2H?

When 70 mL of 0.18 M NH4Cl is added to 70 mL of 0.18 M NH3,relative to the pH of the 0.10 M NH3 solution the pH of the resulting solution will

What is the hydronium ion concentration in a solution prepared by mixing 50.00 mL of 0.10 M HCN with 50.00 mL of NaCN? Assume that the volumes of the solutions are additive and that Ka = 4.9 × 10-10 for HCN.

What is the equation relating the equilibrium constant Kn for the neutralization of a weak acid with a weak base to the Ka of the acid,the Kb of the base and Kw?

Which of these neutralization reactions has a pH > 7 when equal moles of acid and base are mixed?

What is the pH of a solution prepared by mixing 50.00 mL of 0.10 M methylamine,CH₃NH₂,with 15.00 mL of 0.10 M methylammonium chloride,CH₃NH₃Cl? Assume that the volume of the solutions are additive and that K_b = 3.70 × 10^-4 for methylamine.

What is the pH of a solution prepared by mixing 50.00 mL of 0.10 M NH₃ with 20.00 mL of 0.10 M NH₄Cl? Assume that the volume of the solutions are additive and that K_b = 1.8 × 10^-5for NH₃.

What is the pH of a buffer system prepared by dissolving 10.70 grams of NH₄Cl and 30.00 mL of 12 M NH₃ in enough water to make 1.000 L of solution? K_b = 1.80 × 10^-5for NH₃.

What is the pH of a solution prepared by mixing 25.00 mL of 0.10 M CH₃CO₂H with 25.00 mL of 0.040 M CH₃CO₂Na? Assume that the volume of the solutions are additive and that K_a = 1.8 × 10^-5 for CH₃CO₂H.

What is the [CH₃CO₂^-]/[CH₃CO₂H] ratio necessary to make a buffer solution with a pH of 4.24? K_a = 1.8 × 10^-5for CH₃CO₂H.

What is the approximate value of the equilibrium constant,K_n,for the neutralization of acetic acid with potassium hydroxide,shown in the equation below? The K_a for acetic acid is 1.8 × 10^-5. CH₃CO₂H(aq) + KOH(aq) ⇌ H₂O(l) + NaCH₃CO₂(aq)

What is the approximate value of the equilibrium constant,K_n,for the neutralization of hydrochloric acid with sodium hydroxide,shown in the equation below? HBr(aq) + LiOH(aq) ⇌ H₂O(l) + LiBr(aq)

What is the common ion in a solution prepared by mixing 0.55 M LiCH₃CO₂ with 0.10 M CH₃CO₂H?

When 70 mL of 0.18 M NH₄Cl is added to 70 mL of 0.18 M NH₃,relative to the pH of the 0.10 M NH₃solution the pH of the resulting solution will

What is the hydronium ion concentration in a solution prepared by mixing 50.00 mL of 0.10 M HCN with 50.00 mL of NaCN? Assume that the volumes of the solutions are additive and that K_a = 4.9 × 10^-10for HCN.

What is the equation relating the equilibrium constant K_n for the neutralization of a weak acid with a weak base to the K_a of the acid,the K_b of the base and K_w?