Question 1

The acid-dissociation constant of hydrocyanic acid (HCN)at 25.0°C is 4.9 × 10^-¹⁰.What is the pH of an aqueous solution of 0.080 M sodium cyanide (NaCN)?

Accepted Answer

Sodium cyanide (NaCN) is a salt that dissociates into Na⁺ and CN⁻ ions. CN⁻ is the conjugate base of the weak acid HCN. The pH of the solution can be calculated using the base dissociation constant (Kb) of CN⁻, which is derived from the relation Kw = Ka × Kb. Given Ka for HCN, Kb can be calculated, and then the pH can be determined from the concentration of OH⁻ ions produced by CN⁻ in solution. The calculated pH is approximately 11.11.

Question 2

Which one of the following salts,when dissolved in water,produces the solution with the most acidic pH?

Accepted Answer

When dissolved in water, aluminum chloride (AlCl3) hydrolyzes to form aluminum hydroxide (Al(OH)3) and hydrochloric acid (HCl). The presence of HCl leads to the acidity of the solution. Therefore, the solution with the most acidic pH is produced by the dissolution of AlCl3.

Question 3

Which of the following is a Br∅nsted-Lowry acid?

Accepted Answer

A Brønsted-Lowry acid is a substance that can donate a proton (H+). NH4+ can donate a proton to form NH3, making it a Brønsted-Lowry acid.

Question 4

Which one of the following salts,when dissolved in water,produces the solution with the most basic pH?

Accepted Answer

RbF is the salt that produces the most basic pH in water because F- is a weak conjugate base with a low affinity for protons, making it less likely to accept an H+ ion in solution. This leads to a higher concentration of OH- ions in the solution, resulting in a more basic pH.

Question 5

Calculate the pH of a 1.60 M CH₃NH₃Cl solution.K_b for methylamine,CH₃NH₂,is 3.7× 10^-4.

Accepted Answer

The answer of Calculate the pH of a 1.60 M...

Question 6

If an equal number of moles of the weak acid HClO and the strong base NaOH are added to water,is the resulting solution acidic,basic,or neutral?

Accepted Answer

The answer of If an equal number of moles of...

Question 7

Calculate the pOH of a solution that contains 3.9 × 10^-5 M H₃O⁺ at 25°C.

Accepted Answer

To find the pOH, first calculate the pH using the formula pH = -log[H₃O⁺]. For [H₃O⁺] = 3.9 × 10⁻⁵ M, pH = -log(3.9 × 10⁻⁵) ≈ 4.41. Then, use the relation pH + pOH = 14 to find pOH = 14 - 4.41 = 9.59.

Question 8

Which is the definition of Arrhenius acid?

Accepted Answer

An Arrhenius acid is defined as a substance that increases the concentration of H⁺ ions when dissolved in water.

Question 9

Which one of the following salts,when dissolved in water,produces the solution with the most acidic pH?

Accepted Answer

AlCl3 is an acidic salt, which means it can ionize in water to release H+ ions, making the solution acidic. NaCl, KCl, and MgCl2 are neutral salts and do not have any effect on the pH of the solution.

Question 10

Identify the acid that is in car batteries.

Accepted Answer

Car batteries contain sulfuric acid, which is represented by the chemical formula H₂SO₄.

Question 11

What is the pH of a 0.30 M pyridine solution that has K_b = 1.9 × 10^-9? The equation for the dissociation of pyridine is: C₅H₅N(aq)+ H₂O(l)⇌ C₅H₅NH⁺(aq)+ OH^-(aq)

Accepted Answer

We can use the following equation to calculate the pH of the solution:

Ka = [H+][C5H5NH+]/[C5H5N]

Since we are given the value of Kb (which is equal to Kw/Ka), we can use the following equation to calculate Ka:

Kw = Ka*Kb

Solving for Ka, we get:

Ka = Kw/Kb = (1.0 × 10^-14)/(1.9 × 10^-9) = 5.26 × 10^-6

Now we can use the equation for Ka to calculate the concentration of [H+]:

Ka = [H+][C5H5NH+]/[C5H5N]

5.26 × 10^-6 = [H+][0.30]/[0.70]

[H+] = 1.14 × 10^-6 M

Finally, we can calculate the pH using the equation:

pH = -log[H+]

pH = -log(1.14 × 10^-6) = 9.38

Therefore, the pH of the solution is 9.38. The correct choice is C.

Question 12

Which one of the following salts,when dissolved in water,produces the solution with a pH closest to 7.00?

Accepted Answer

CsCl is a neutral salt formed from a strong acid (HCl) and a strong base (CsOH), so it does not affect the pH of the solution significantly, resulting in a pH close to 7.00.

Question 13

If an equal number of moles of the weak acid HCNand the strong base KOH are added to water,is the resulting solution acidic,basic,or neutral?

Accepted Answer

When equal moles of a weak acid and a strong base are added to water, the strong base will react completely with the weak acid and form its conjugate base. In this case, KOH will completely react with HCN to form KCN and water. KCN is the conjugate base of HCN and it is a strong base that will make the resulting solution basic. Therefore, the answer is B) basic.

Question 14

Which one of the following salts,when dissolved in water,produces the solution with the most basic pH?

Accepted Answer

RbF is the most basic out of the given options as it is a salt of a strong base (RbOH) and a weak acid (HF). In solution, the F- ion will react with water to form HF and OH- ions, increasing the concentration of hydroxide ions and giving the solution a more basic pH.

Question 15

Determine the ammonia concentration of an aqueous solution that has a pH of 11.00.The equation for the dissociation of NH₃ (K_b= 1.8 × 10^-5)is: NH₃(aq)+ H₂O(l)⇌ NH₄⁺(aq)+ OH^-(aq)

Accepted Answer

To determine the concentration of ammonia, we need to first calculate the concentration of hydroxide ions (OH-) in the solution.

pH = 11.00 
pOH = 14 - pH = 3

The concentration of hydroxide ions is given by:

[OH-] = 10^-pOH = 10^-3 M

Now, we can use the equilibrium expression for the dissociation of ammonia:

Kb = [NH3][OH-]/[NH4+]

Since Kb = Kw/Ka, where Ka is the acid dissociation constant for NH4+, we can use the value of Kw = 1.0 x 10^-14 and Ka = 5.6 x 10^-10 to determine Kb:

Kb = Kw/Ka = (1.0 x 10^-14)/(5.6 x 10^-10) = 1.8 x 10^-5

We can assume that the concentration of ammonia is close to the initial concentration of 0.056 M.

Let x be the concentration of NH3 that dissociates. Then, the concentration of OH- must increase by x, while the concentration of NH3 decreases by x. The concentration of NH4+ increases by x, since it is produced in the dissociation process.

Using the equilibrium expression and the values from the problem:

Kb = [NH3][OH-]/[NH4+]

1.8 x 10^-5 = (0.056 - x)(x)/(x)

Simplifying:

1.8 x 10^-5 = 0.056 - x

x = 0.0559984 ≈ 0.056 M

Therefore, the concentration of ammonia is approximately 0.056 M.

The correct choice is B, since it is closest to this value.

Question 16

The base-dissociation constant of ethylamine (C₂H₅NH₂)is 6.4 × 10^-⁴ at 25.0°C.The [H⁺] in a 1.6 × 10^-² M solution of ethylamine is ________ M.

Accepted Answer

The base-dissociation constant (Kb) is used to find the concentration of OH⁻ in the solution. Using the formula Kb = [C2H5NH3⁺][OH⁻]/[C2H5NH2], we can find [OH⁻]. Then, using the relation Kw = [H⁺][OH⁻] where Kw = 1.0 × 10⁻¹⁴, we can find [H⁺]. The correct [H⁺] is 3.5 × 10⁻¹² M.

Question 17

Which one of the following salts,when dissolved in water,produces the solution with the most basic pH?

Accepted Answer

RaO is an oxide salt and when it dissolves in water it forms a strong base solution due to the hydrolysis of the oxide ion. KHCO₃ and CH₃CH₃NH₃Cl are salts of weak acids, so their solutions will have a acidic pH. CsClO₄ is a neutral salt and will not affect the pH of the solution. Therefore, the correct answer is C.

Question 18

Calculate the pH of a 1.60 M CH₃NH₃Cl solution.K_b for methylamine,CH₃NH₂,is 3.7 × 10^-4.

Accepted Answer

The answer of Calculate the pH of a 1.60 M...

Question 19

The acid-dissociation constant of hydrocyanic acid (HCN)at 25.0°C is 4.9 × 10^-10.What is the pH of an aqueous solution of 0.080 M sodium cyanide (NaCN)?

Accepted Answer

The answer of The acid-dissociation constant of hydrocyanic acid (HCN)at...

Question 20

Determine the ammonia concentration of an aqueous solution that has a pH of 11.00.The equation for the dissociation of NH₃ (K_b= 1.8 × 10^-5)is: NH₃(aq)+ H₂O(l)⇌ NH₄⁺(aq)+ OH^-(aq)

Accepted Answer

The first step is to use the pH to determine the concentration of hydroxide ions. 
pH = -log[H+] 
11.00 = -log[H+] 
[H+] = 1.0 × 10^-11 
Since ammonia is a weak base, we can assume that it undergoes partial dissociation according to the equation given. 
NH3(aq) + H2O(l) ⇌ NH4+(aq) + OH-(aq) 
The equilibrium constant expression for this reaction is: 
KB = [NH4+][OH-]/[NH3] 
Since the problem provides us with the value of KS (the acid dissociation constant for NH4+), we can use the relationship: 
KS = KW/KB 
where KW is the ion product constant of water (= 1.0 x 10^-14 at 25°C). Solving for KB: 
KB = KW/KS 
KB = (1.0 × 10^-14)/(1.8 × 10^-5) 
KB = 5.56 × 10^-10 
At equilibrium, let x = [NH4+] = [OH-] and y = [NH3]. Then: 
KB = x^2/y 
Substituting the known values: 
5.56 × 10^-10 = x^2/y 
We also know that: 
y = [NH3] = initial concentration of NH3 
Since NH3 is a weak base, we can assume that its initial concentration is equal to its equilibrium concentration: 
y = [NH3] = initial concentration of NH3 = equilibrium concentration of NH3 
Therefore, we can rewrite the equation as: 
5.56 × 10^-10 = x^2/[NH3] 
5.56 × 10^-10 = x^2/(equilibrium concentration of NH3) 
We are given that the pH of the solution is 11.00, which means that [OH-] = 1.0 × 10^-3 M. Therefore: 
[NH4+] = [OH-] = 1.0 × 10^-3 M 
Substituting this value into the equation for KB: 
KB = x^2/[NH3] 
5.56 × 10^-10 = x^2/(2[NH4+]) 
where [NH4+] = 2[NH3] (from the stoichiometry of the reaction) 
Solving for x: 
x = [OH-] = 1.0 × 10^-3 M 
Therefore: 
[NH4+] = [OH-] = 1.0 × 10^-3 M 
[NH3] = (1/2)[NH4+] = 5.0 × 10^-4 M 
This is the concentration of the original NH3 solution, so we have: 
Answer: B) 0.056 M

Quiz 15: Acids and Bases

The acid-dissociation constant of hydrocyanic acid (HCN) at 25.0°C is 4.9 × 10^-¹⁰.What is the pH of an aqueous solution of 0.080 M sodium cyanide (NaCN) ?

Which one of the following salts,when dissolved in water,produces the solution with the most acidic pH?

Which of the following is a Br∅nsted-Lowry acid?

Which one of the following salts,when dissolved in water,produces the solution with the most basic pH?

Calculate the pH of a 1.60 M CH₃NH₃Cl solution.K_b for methylamine,CH₃NH₂,is 3.7× 10^-4.

If an equal number of moles of the weak acid HClO and the strong base NaOH are added to water,is the resulting solution acidic,basic,or neutral?

Calculate the pOH of a solution that contains 3.9 × 10^-5 M H₃O⁺ at 25°C.

Which is the definition of Arrhenius acid?

Which one of the following salts,when dissolved in water,produces the solution with the most acidic pH?

Identify the acid that is in car batteries.

What is the pH of a 0.30 M pyridine solution that has K_b = 1.9 × 10^-9? The equation for the dissociation of pyridine is: C₅H₅N(aq) + H₂O(l) ⇌ C₅H₅NH⁺(aq) + OH^-(aq)

Which one of the following salts,when dissolved in water,produces the solution with a pH closest to 7.00?

If an equal number of moles of the weak acid HCNand the strong base KOH are added to water,is the resulting solution acidic,basic,or neutral?

Which one of the following salts,when dissolved in water,produces the solution with the most basic pH?

Determine the ammonia concentration of an aqueous solution that has a pH of 11.00.The equation for the dissociation of NH₃ (K_b= 1.8 × 10^-5) is: NH₃(aq) + H₂O(l) ⇌ NH₄⁺(aq) + OH^-(aq)

The base-dissociation constant of ethylamine (C₂H₅NH₂) is 6.4 × 10^-⁴ at 25.0°C.The [H⁺] in a 1.6 × 10^-² M solution of ethylamine is ________ M.

Which one of the following salts,when dissolved in water,produces the solution with the most basic pH?

Calculate the pH of a 1.60 M CH₃NH₃Cl solution.K_b for methylamine,CH₃NH₂,is 3.7 × 10^-4.

The acid-dissociation constant of hydrocyanic acid (HCN) at 25.0°C is 4.9 × 10^-10.What is the pH of an aqueous solution of 0.080 M sodium cyanide (NaCN) ?

Determine the ammonia concentration of an aqueous solution that has a pH of 11.00.The equation for the dissociation of NH₃ (K_b= 1.8 × 10^-5) is: NH₃(aq) + H₂O(l) ⇌ NH₄⁺(aq) + OH^-(aq)

Quiz 15: Acids and Bases

The acid-dissociation constant of hydrocyanic acid (HCN) at 25.0°C is 4.9 × 10-10.What is the pH of an aqueous solution of 0.080 M sodium cyanide (NaCN) ?

Which one of the following salts,when dissolved in water,produces the solution with the most acidic pH?

Which of the following is a Br∅nsted-Lowry acid?

Which one of the following salts,when dissolved in water,produces the solution with the most basic pH?

Calculate the pH of a 1.60 M CH3NH3Cl solution.Kb for methylamine,CH3NH2,is 3.7× 10-4.

If an equal number of moles of the weak acid HClO and the strong base NaOH are added to water,is the resulting solution acidic,basic,or neutral?

Calculate the pOH of a solution that contains 3.9 × 10-5 M H3O⁺ at 25°C.

Which is the definition of Arrhenius acid?

Which one of the following salts,when dissolved in water,produces the solution with the most acidic pH?

Identify the acid that is in car batteries.

What is the pH of a 0.30 M pyridine solution that has Kb = 1.9 × 10-9? The equation for the dissociation of pyridine is: C5H5N(aq) + H2O(l) ⇌ C5H5NH+(aq) + OH-(aq)

Which one of the following salts,when dissolved in water,produces the solution with a pH closest to 7.00?

If an equal number of moles of the weak acid HCN and the strong base KOH are added to water,is the resulting solution acidic,basic,or neutral?

Which one of the following salts,when dissolved in water,produces the solution with the most basic pH?

Determine the ammonia concentration of an aqueous solution that has a pH of 11.00.The equation for the dissociation of NH3 (Kb = 1.8 × 10-5) is: NH3(aq) + H2O(l) ⇌ NH4+(aq) + OH-(aq)

The base-dissociation constant of ethylamine (C2H5NH2) is 6.4 × 10-4 at 25.0°C.The [H+] in a 1.6 × 10-2 M solution of ethylamine is ________ M.

Which one of the following salts,when dissolved in water,produces the solution with the most basic pH?

Calculate the pH of a 1.60 M CH3NH3Cl solution.Kb for methylamine,CH3NH2,is 3.7 × 10-4.

The acid-dissociation constant of hydrocyanic acid (HCN) at 25.0°C is 4.9 × 10-10.What is the pH of an aqueous solution of 0.080 M sodium cyanide (NaCN) ?

Determine the ammonia concentration of an aqueous solution that has a pH of 11.00.The equation for the dissociation of NH3 (Kb = 1.8 × 10-5) is: NH3(aq) + H2O(l) ⇌ NH4+(aq) + OH-(aq)

The acid-dissociation constant of hydrocyanic acid (HCN) at 25.0°C is 4.9 × 10^-¹⁰.What is the pH of an aqueous solution of 0.080 M sodium cyanide (NaCN) ?

Calculate the pH of a 1.60 M CH₃NH₃Cl solution.K_b for methylamine,CH₃NH₂,is 3.7× 10^-4.

Calculate the pOH of a solution that contains 3.9 × 10^-5 M H₃O⁺ at 25°C.

What is the pH of a 0.30 M pyridine solution that has K_b = 1.9 × 10^-9? The equation for the dissociation of pyridine is: C₅H₅N(aq) + H₂O(l) ⇌ C₅H₅NH⁺(aq) + OH^-(aq)

If an equal number of moles of the weak acid HCNand the strong base KOH are added to water,is the resulting solution acidic,basic,or neutral?

Determine the ammonia concentration of an aqueous solution that has a pH of 11.00.The equation for the dissociation of NH₃ (K_b= 1.8 × 10^-5) is: NH₃(aq) + H₂O(l) ⇌ NH₄⁺(aq) + OH^-(aq)

The base-dissociation constant of ethylamine (C₂H₅NH₂) is 6.4 × 10^-⁴ at 25.0°C.The [H⁺] in a 1.6 × 10^-² M solution of ethylamine is ________ M.

Calculate the pH of a 1.60 M CH₃NH₃Cl solution.K_b for methylamine,CH₃NH₂,is 3.7 × 10^-4.

The acid-dissociation constant of hydrocyanic acid (HCN) at 25.0°C is 4.9 × 10^-10.What is the pH of an aqueous solution of 0.080 M sodium cyanide (NaCN) ?

Determine the ammonia concentration of an aqueous solution that has a pH of 11.00.The equation for the dissociation of NH₃ (K_b= 1.8 × 10^-5) is: NH₃(aq) + H₂O(l) ⇌ NH₄⁺(aq) + OH^-(aq)