Question 1

What is the conjugate acid of HS-?

Accepted Answer

The conjugate acid of HS- is formed by adding a proton (H+) to HS-, resulting in H₂S. Choice A is not a valid chemical formula. Choice B is a combination of sulfur-containing ions but does not represent the conjugate acid of HS-. Choice C is the original acid and not the conjugate. Choice E represents a different molecule.

Question 2

The ammonium ion,NH₄⁺,is a weak acid.

Accepted Answer

The ammonium ion, NH4+, can act as a weak acid by donating a proton (H+) to a water molecule, forming the hydronium ion (H3O+).

Question 3

Carboxylic acids are _____.

Accepted Answer

Carboxylic acids are always weak acids because the carboxyl group (COOH) donates a proton (H+) to water to form the hydronium ion (H3O+) and the carboxylate ion (RCOO-), resulting in a low dissociation constant (Ka).

Question 4

Which of the following is the correct Kb expression for the reaction below? B(aq)+ H₂O (l) HB+(aq)+ OH^-(aq)

Accepted Answer

The answer of Which of the following is the correct...

Question 5

Which represents a weak base B with K_b= 2 ×10^-³? (Each circle represents 1.0 ×10^-³ mol of atoms,and the volume of each box is 1.0 L.Solvent water molecules are not shown for clarity.)

Accepted Answer

The answer of Which represents a weak base B with...

Question 6

Which of the following species can act as a Lewis acid?

Accepted Answer

BF3 is a Lewis acid because it can accept a pair of electrons.

Question 7

What mass of sodium nitrite must be added to enough water to make 350.0 mL of a solution with pH = 8.40? [K_a(HNO₂)= 5.6 × 10^-⁴]

Accepted Answer

To find the mass of sodium nitrite, we first calculate the concentration of OH⁻ using the pH, then use the Kb of nitrite to find the concentration of nitrite ions. Finally, we calculate the mass using the molar mass of sodium nitrite.

Question 8

Weak acids have weak conjugate bases.

Accepted Answer

Weak acids have strong conjugate bases. The strength of an acid and its conjugate base are inversely related.

Question 9

Which one of these responses is true with regard to a 0.1 M solution of a weak acid HA?

Accepted Answer

A 0.1 M solution of a weak acid HA will not completely dissociate, so the concentration of [H+] in solution will be less than 0.1 M, leading to a pH greater than 1.0. Therefore, option D is the correct answer. Option A is not true because [H⁺] cannot be greater than the concentration of the original solution (0.1 M). Option B is not true because a pH of 1.0 corresponds to a strong acid, not a weak acid. Option C is not necessarily true, as it depends on the equilibrium constant for the acid dissociation. Option E is not true because the concentration of [OH-] does not necessarily need to be greater than the concentration of [H+].

Question 10

Below is a representation of an aqueous solution of a weak acid HA at equilibrium.(Each circle represents 1.0 ×10^-3 mol of atoms,and the volume of the box is 1.0 L.Solvent water molecules are not shown for clarity.) What is the pH of the solution?

Accepted Answer

The pH of a solution of a weak acid can be calculated using the expression pH = pKa + log([A-]/[HA]), where pKa is the acid dissociation constant, [A-] is the concentration of the conjugate base, and [HA] is the concentration of the acid. In this case, the weak acid is represented by the circles, and the conjugate base (A-) is represented by the dots. From the diagram, we can see that the concentration of the conjugate base is roughly 1/10th the concentration of the acid, so [A-]/[HA] is approximately equal to 0.1. The pKa of the weak acid can be estimated to be around 4.7 based on the pH scale shown in the diagram. Plugging these values into the pH expression gives pH = 4.7 + log(0.1) = 3.

Question 11

The stronger the acid,the weaker its conjugate base.

Accepted Answer

This is a fundamental principle of acid-base chemistry known as the Bronsted-Lowry theory. The strength of an acid is determined by its ability to donate a proton (H+), while the strength of its conjugate base is determined by its ability to accept a proton. Therefore, a strong acid will readily donate a proton, leaving behind a weak conjugate base that is unable to accept another proton. On the other hand, a weak acid will only partially donate a proton, leaving behind a stronger conjugate base that is capable of accepting another proton.

Question 12

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

Accepted Answer

Diluting a strong acid such as HCl with water will not increase its pH above 7, as it will still be an acidic solution. The pH may be higher than the undiluted acid, but it will still be acidic and have a pH of less than 7.

Question 13

Which statement is true regarding the reversible reaction below? H₂CO₃+ F^- HCO₃+ HF.K_a1(H₂CO₃)= 4.2 × 10^-⁷; K_a(HF)= 7.1 × 10^-⁴

Accepted Answer

The answer of Which statement is true regarding the reversible...

Question 14

Below is a representation of an aqueous solution of a weak acid HA at equilibrium.(Each circle represents 1.0 mmol of atoms,and the volume of the box is 1.0 L.Solvent water molecules are not shown for clarity.)  What is the percent ionization of HA?

Accepted Answer

The percent ionization of a weak acid is equal to the concentration of ionized acid divided by the initial concentration of acid, multiplied by 100%. In the given diagram, there are a total of 4.0 mmol of HA and 1.0 mmol of A-. Since HA <--> H+ + A-, the concentration of ionized acid (A-) is equal to [A-] = 1.0 mmol/L. Therefore, the percent ionization is (1.0 mmol/L)/(4.0 mmol/L) x 100% = 25%. The correct answer is C.

Question 15

Below is a representation of an aqueous solution of a weak acid HA at equilibrium.(Each circle represents 1.0 ×10^-³ mol of atoms,and the volume of the box is 1.0 L.Solvent water molecules are not shown for clarity.) What is K_a of HA?

Accepted Answer

The answer of Below is a representation of an aqueous...

Question 16

Which diagram best represents the products when equimolar amounts of HF(g)and NH₃(g)react?

Accepted Answer

The answer of Which diagram best represents the products when...

Question 17

All strong acids have weak conjugate bases.

Accepted Answer

This statement is true according to the Bronsted-Lowry theory of acids and bases. When a strong acid donates a proton (H+) to a water molecule, it forms a weak conjugate base. This is because the weaker the acid, the stronger its conjugate base. For example, the strong acid HCl has a weak conjugate base of Cl-. Similarly, the strong acid H2SO4 has a weak conjugate base of HSO4-.

Question 18

Equal volumes of two solutions,one containing a strong acid at pH 2 and the other containing a strong base at pH 12,are mixed.Once equilibrium is achieved,what is the final pH of the combined solution?

Accepted Answer

When the strong acid and strong base are mixed, they neutralize each other and form a salt and water. The pH of this solution will be neutral, which is 7.

Question 19

Which of the following salts will form an acidic solution when dissolved in water?

Accepted Answer

NH₄NO₃ will form an acidic solution because NH₄⁺ is the conjugate acid of NH₃, a weak base, and will donate protons to water, increasing the H⁺ concentration.

Question 20

Below is a representation of pure liquid HX,an amphoteric substance,at equilibrium.(Each circle represents 1.0 ×10^-³ mol of atoms,and the volume of the box is 1.0 L.) What is the autoionization constant for HX?

Accepted Answer

The answer of Below is a representation of pure liquid...

Quiz 16: Acids and Bases

What is the conjugate acid of HS-?

The ammonium ion,NH₄⁺,is a weak acid.

Carboxylic acids are _____.

Which of the following is the correct Kb expression for the reaction below? B(aq) + H₂O (l) HB+(aq) + OH^-(aq)

Which represents a weak base B with K_b= 2 ×10^-³? (Each circle represents 1.0 ×10^-³ mol of atoms,and the volume of each box is 1.0 L.Solvent water molecules are not shown for clarity.)

Which of the following species can act as a Lewis acid?

What mass of sodium nitrite must be added to enough water to make 350.0 mL of a solution with pH = 8.40? [K_a(HNO₂) = 5.6 × 10^-⁴]

Weak acids have weak conjugate bases.

Which one of these responses is true with regard to a 0.1 M solution of a weak acid HA?

Below is a representation of an aqueous solution of a weak acid HA at equilibrium.(Each circle represents 1.0 ×10^-3 mol of atoms,and the volume of the box is 1.0 L.Solvent water molecules are not shown for clarity.) What is the pH of the solution?

The stronger the acid,the weaker its conjugate base.

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

Which statement is true regarding the reversible reaction below? H₂CO₃+ F^- HCO₃+ HF.K_a1(H₂CO₃) = 4.2 × 10^-⁷; K_a(HF) = 7.1 × 10^-⁴

Below is a representation of an aqueous solution of a weak acid HA at equilibrium.(Each circle represents 1.0 mmol of atoms,and the volume of the box is 1.0 L.Solvent water molecules are not shown for clarity.) What is the percent ionization of HA?

Below is a representation of an aqueous solution of a weak acid HA at equilibrium.(Each circle represents 1.0 ×10^-³ mol of atoms,and the volume of the box is 1.0 L.Solvent water molecules are not shown for clarity.) What is K_a of HA?

Which diagram best represents the products when equimolar amounts of HF(g) and NH₃(g) react?

All strong acids have weak conjugate bases.

Equal volumes of two solutions,one containing a strong acid at pH 2 and the other containing a strong base at pH 12,are mixed.Once equilibrium is achieved,what is the final pH of the combined solution?

Which of the following salts will form an acidic solution when dissolved in water?

Below is a representation of pure liquid HX,an amphoteric substance,at equilibrium.(Each circle represents 1.0 ×10^-³ mol of atoms,and the volume of the box is 1.0 L.) What is the autoionization constant for HX?

Quiz 16: Acids and Bases

What is the conjugate acid of HS-?

The ammonium ion,NH4+,is a weak acid.

Carboxylic acids are _____.

Which of the following is the correct Kb expression for the reaction below? B(aq) + H2O (l) HB+(aq) + OH-(aq)

Which represents a weak base B with Kb= 2 ×10-3? (Each circle represents 1.0 ×10-3 mol of atoms,and the volume of each box is 1.0 L.Solvent water molecules are not shown for clarity.)

Which of the following species can act as a Lewis acid?

What mass of sodium nitrite must be added to enough water to make 350.0 mL of a solution with pH = 8.40? [Ka(HNO2) = 5.6 × 10-4]

Weak acids have weak conjugate bases.

Which one of these responses is true with regard to a 0.1 M solution of a weak acid HA?

Below is a representation of an aqueous solution of a weak acid HA at equilibrium.(Each circle represents 1.0 ×10-3 mol of atoms,and the volume of the box is 1.0 L.Solvent water molecules are not shown for clarity.) What is the pH of the solution?

The stronger the acid,the weaker its conjugate base.

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

Which statement is true regarding the reversible reaction below? H2CO3+ F- HCO3+ HF.Ka1(H2CO3) = 4.2 × 10-7; Ka(HF) = 7.1 × 10-4

Below is a representation of an aqueous solution of a weak acid HA at equilibrium.(Each circle represents 1.0 mmol of atoms,and the volume of the box is 1.0 L.Solvent water molecules are not shown for clarity.) What is the percent ionization of HA?

Below is a representation of an aqueous solution of a weak acid HA at equilibrium.(Each circle represents 1.0 ×10-3 mol of atoms,and the volume of the box is 1.0 L.Solvent water molecules are not shown for clarity.) What is Ka of HA?

Which diagram best represents the products when equimolar amounts of HF(g) and NH3(g) react?

All strong acids have weak conjugate bases.

Equal volumes of two solutions,one containing a strong acid at pH 2 and the other containing a strong base at pH 12,are mixed.Once equilibrium is achieved,what is the final pH of the combined solution?

Which of the following salts will form an acidic solution when dissolved in water?

Below is a representation of pure liquid HX,an amphoteric substance,at equilibrium.(Each circle represents 1.0 ×10-3 mol of atoms,and the volume of the box is 1.0 L.) What is the autoionization constant for HX?

The ammonium ion,NH₄⁺,is a weak acid.

Which of the following is the correct Kb expression for the reaction below? B(aq) + H₂O (l) HB+(aq) + OH^-(aq)

Which represents a weak base B with K_b= 2 ×10^-³? (Each circle represents 1.0 ×10^-³ mol of atoms,and the volume of each box is 1.0 L.Solvent water molecules are not shown for clarity.)

What mass of sodium nitrite must be added to enough water to make 350.0 mL of a solution with pH = 8.40? [K_a(HNO₂) = 5.6 × 10^-⁴]

Below is a representation of an aqueous solution of a weak acid HA at equilibrium.(Each circle represents 1.0 ×10^-3 mol of atoms,and the volume of the box is 1.0 L.Solvent water molecules are not shown for clarity.) What is the pH of the solution?

Which statement is true regarding the reversible reaction below? H₂CO₃+ F^- HCO₃+ HF.K_a1(H₂CO₃) = 4.2 × 10^-⁷; K_a(HF) = 7.1 × 10^-⁴

Below is a representation of an aqueous solution of a weak acid HA at equilibrium.(Each circle represents 1.0 ×10^-³ mol of atoms,and the volume of the box is 1.0 L.Solvent water molecules are not shown for clarity.) What is K_a of HA?

Which diagram best represents the products when equimolar amounts of HF(g) and NH₃(g) react?

Below is a representation of pure liquid HX,an amphoteric substance,at equilibrium.(Each circle represents 1.0 ×10^-³ mol of atoms,and the volume of the box is 1.0 L.) What is the autoionization constant for HX?