Question 1

A) Write a balanced equation representing the reaction of the acid, H₂PO₄¯ with the base, water. B) Write the expression for K_a of H₂PO₄¯ in terms of concentrations of relevant species.

Accepted Answer

The answer of A) Write a balanced equation representing the...

Question 2

Define an acid according to the Arrhenius theory, and write a balanced equation to support this definition.

Accepted Answer

The answer of Define an acid according to the Arrhenius...

Question 3

K_w = 1.0 *10¯¹⁴, regardless of temperature.

Accepted Answer

The value of K_w (the ion product of water) changes with temperature. It is 1.0 * 10^-14 at 25°C, but varies at other temperatures.

Question 4

The pH of a 0.200 M solution of the weak base pyridine, C₅H₅N, is 8.59. A) Draw up a reaction table for the reaction of 0.200 M pyridine with water B) Calculate K_b.

Accepted Answer

The answer of The pH of a 0.200 M solution...

Question 5

If a strong acid such as HCl is diluted sufficiently with water, the pH will be higher than 7.

Accepted Answer

Dilution of a strong acid with water will result in a decrease in the concentration of H+ ions, but the pH will still be below 7, as the solution is still acidic.

Question 6

Define an acid according to the Lewis theory. Write a balanced equation in support of this definition, in which the acid is neither an Arrhenius acid nor a Brønsted-Lowry acid.

Accepted Answer

The answer of Define an acid according to the Lewis...

Question 7

Which one of the following is a Lewis acid but not a Brønsted-Lowry acid?

Accepted Answer

A Lewis acid is a substance that can accept a pair of electrons, while a Brønsted-Lowry acid is a substance that can donate a proton (H+). Fe³⁺ can act as a Lewis acid because it can accept a pair of electrons, but it cannot donate a proton and therefore cannot act as a Brønsted-Lowry acid. The other choices all have a hydrogen atom that can donate a proton, making them both Lewis and Brønsted-Lowry acids.

Question 8

All strong acids have weak conjugate bases.

Accepted Answer

Strong acids completely dissociate in water, leaving behind a very weak conjugate base. This is the basis for the Bronsted-Lowry acid-base theory.

Question 9

All Brønsted-Lowry bases have at least one lone pair of electrons.

Accepted Answer

According to the Brønsted-Lowry theory, a base is a substance that accepts a proton (H+ ion). In order to do so, the base must have at least one lone pair of electrons to form a bond with the proton. Therefore, all Brønsted-Lowry bases have at least one lone pair of electrons.

Question 10

Arrhenius bases raise the hydroxide ion concentration when dissolved in water.

Accepted Answer

This is the definition of Arrhenius bases. They dissociate in water to release hydroxide ions, which increase the concentration of OH- in the solution.

Question 11

If the compound HX is a strong acid (where H is the acidic proton in this acid), then the ion X¯ is a weak base.

Accepted Answer

This statement is true according to the Bronsted-Lowry theory of acids and bases. A strong acid completely dissociates in water to form H+ ions, leaving X- ions as the conjugate base. Since the strong acid has donated its proton easily, it follows that the conjugate base must be a weak base as it is less likely to accept a proton.

Question 12

It is not possible to have a pH lying outside the range 0 to 14.

Accepted Answer

The pH scale typically ranges from 0 to 14 for aqueous solutions, but it can go below 0 or above 14 for extremely acidic or basic solutions, respectively.

Question 13

Formic acid, HCOOH, is a weak acid with a pK_a of 3.74. A) Draw a reaction table for the reaction of 0.300 M formic acid with water. B) Calculate the pH of this solution.

Accepted Answer

The answer of Formic acid, HCOOH, is a weak acid...

Question 14

In order to be a Brønsted-Lowry base, a species must contain a proton.

Accepted Answer

In order to be a Brønsted-Lowry base, a species must be able to accept a proton, not necessarily contain one.

Question 15

Define a base according to the Brønsted-Lowry theory. Write a balanced equation in support of this definition, in which the base is acting as a Brønsted-Lowry base but not as an Arrhenius base.

Accepted Answer

The answer of Define a base according to the Brønsted-Lowry...

Question 16

All weak acids have strong conjugate bases.

Accepted Answer

Weak acids have weak conjugate bases, not strong ones, because the strength of a conjugate base is inversely related to the strength of its acid. Strong acids have weak conjugate bases, and weak acids have relatively stronger, but still generally weak, conjugate bases.

Question 17

Describe what is meant by the "leveling effect." Use a real acid as an example, and write an appropriate equation.

Accepted Answer

The answer of Describe what is meant by the "leveling...

Question 18

Consider the reaction: BF₃ + F¯ $\rightarrow$ BF₄¯ Can this ever be considered to be an acid-base reaction? Support your answer with appropriate arguments.

Accepted Answer

The answer of Consider the reaction: BF₃ + F¯ $\rightarrow$...

Question 19

All Brønsted-Lowry bases contain the hydroxide ion, OH¯.

Accepted Answer

False - Brønsted-Lowry bases can accept a proton (H+) without necessarily containing the hydroxide ion. For example, ammonia (NH3) can act as a weak base by accepting a proton to form ammonium ion (NH4+), without any involvement of hydroxide ion.

Question 20

The English are fond of soggy French fries ("chips") wrapped in old newspaper and generously drenched in vinegar, which is a 0.83 M solution of acetic acid. If the acetic acid in vinegar is 0.47% dissociated, calculate K_a for this acid.

Accepted Answer

The answer of The English are fond of soggy French...

Quiz 18: Acid-Base Equilibria

A) Write a balanced equation representing the reaction of the acid, H2PO4¯ with the base, water. B) Write the expression for Ka of H2PO4¯ in terms of concentrations of relevant species.