Question 1

Due to a highway accident, 150 L of concentrated hydrochloric acid (12.0 M)is released into a lake containing 5.0 × 10⁵ m³ of water.If the pH of this lake was 7.0 prior to the accident, what is the pH of the lake following the accident?

Accepted Answer

The moles of HCl added are 1800 moles (150 L * 12.0 M). The concentration of H+ ions in the lake becomes 3.6 x 10^-3 M (1800 moles / 5.0 x 10^5 m^3). The pH is calculated as -log(3.6 x 10^-3), which is approximately 5.44.

Question 2

Aspartic acid (C₄H₇NO₄), one of the 20 essential amino acids, has two ionizable hydrogens.At 25°C, K_a1 = 1.38 × 10^-4 and K_a2 = 1.51 × 10^-10.What is the concentration of doubly ionized aspartate ions in a 0.125 M aqueous solution of aspartic acid?

Accepted Answer

The answer of Aspartic acid (C₄H₇NO₄), one of the 20...

Question 3

What is the pH of a solution prepared by mixing 50.0 mL of 0.300 M HCl with 450.0 mL of 0.400 M HIO₃? [K_a(HIO₃)= 1.6 × 10^-1]

Accepted Answer

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

Question 4

What mass of potassium hypochlorite must be added to 450.mL of water to give a solution with pH = 10.20? [K_a(HClO)= 4.0 × 10^-8]

Accepted Answer

To find the mass of potassium hypochlorite (KClO) needed, we first determine the concentration of ClO⁻ ions required for the desired pH using the formula pH = pKa + log([A⁻]/[HA]). Given pH = 10.20 and pKa = 7.40 (from Ka), we solve for [ClO⁻]. Then, using the molar mass of KClO, we calculate the mass needed for the 450 mL solution.

Question 5

What is the pH of a solution prepared by mixing 100.mL of 0.0500 M HCl with 300.mL of 0.500 M HF? [K_a(HF)= 7.1 × 10^-4]

Accepted Answer

The solution is a mixture of a strong acid (HCl) and a weak acid (HF). The concentration of HCl is 0.0125 M after dilution, and HF is 0.375 M. The pH is mainly determined by the strong acid, HCl, but HF also contributes. Using the Henderson-Hasselbalch equation for HF and considering the contribution of HCl, the pH is approximately 1.63.

Question 6

For maleic acid, HOOCCH=CHCOOH, K_a1 = 1.42 × 10^-2 and K_a2 = 8.57 × 10^-7. What is the concentration of maleate ion (^-OOCCH=CHCOO^-)in a 0.150 M aqueous solution of maleic acid?

Accepted Answer

The answer of For maleic acid, HOOCCH=CHCOOH, K_a1 = 1.42...

Question 7

Identify the conjugate acid-base pairs in the reaction HSO₄^- + HF H₂SO₄ + F^- One conjugate acid-base pair is _______________; the other acid-base pair is ______________.

Accepted Answer

The answer of Identify the conjugate acid-base pairs in the...

Question 8

Which one of these salts will form an acidic solution upon dissolving in water?

Accepted Answer

The answer of Which one of these salts will form...

Question 9

A tablet of a common over-the-counter drug contains 200.mg of caffeine (C₈H₁₀N₄O₂).What is the pH of the solution resulting from the dissolution of two of these tablets in 225.mL of water? (For caffeine, K_b = 4.1 × 10^-4.)

Accepted Answer

The answer of A tablet of a common over-the-counter drug...

Question 10

Which one of the following salts will form an acidic solution on dissolving in water?

Accepted Answer

The answer of Which one of the following salts will...

Question 11

The equilibrium constant for the reaction C₇H₁₅COOH(aq)+ HCOO^-(aq) C₇H₁₅COO^-(aq)+ HCOOH(aq) Is 7.23 × 10^-2 at 25°C.If K_a for formic acid (HCOOH)is 1.77 × 10^-4, what is the acid dissociation constant for C₇H₁₅COOH?

Accepted Answer

The answer of The equilibrium constant for the reaction C₇H₁₅COOH(aq)+...

Question 12

The equilibrium constant for the reaction C₆H₅COOH(aq)+ CH₃COO^-(aq) C₆H₅COO^-(aq)+ CH₃COOH(aq) Is 3.6 at 25°C.If K_a for CH₃COOH is 1.8 × 10^-5, what is the acid dissociation constant for C₆H₅COOH?

Accepted Answer

The acid dissociation constant (Ka) for the given reaction is equal to the ion product constant (KW) divided by the equilibrium constant (Kc) for the reaction.

KW = 1.0 × 10^-14 (at 25°C)
Kc = 3.6 (given)

Therefore, Ka = KW/Kc = 1.8 × 10^-5 / 3.6 = 5.0 × 10^-6

The closest choice to this value is B, 6.5 × 10^-5, making it the correct answer.

Question 13

What mass of ammonium chloride must be added to 250.mL of water to give a solution with pH = 4.85? [K_b(NH₃)= 1.8 × 10^-5]

Accepted Answer

To find the mass of NH4Cl needed, we first calculate the concentration of H+ ions using the pH. Then, using the Kb of NH3, we find the concentration of NH4+ needed to achieve this pH. Finally, we convert this concentration to mass using the molar mass of NH4Cl.

Question 14

The hydrolysis of NH₄F will result in which of the following types of solutions given: (K_a(NH₄⁺)= 5.6 x 10^-10, K_b(F^-)= 1.4 x 10^-11)

Accepted Answer

The hydrolysis of NH₄F will release H+ ions, making the solution acidic.

Question 15

What mass of sodium cyanide must be added to 250.mL of water in order to obtain a solution having a pH of 10.50? [K_a(HCN)= 4.9 × 10^-10]

Accepted Answer

To calculate the number of moles of HCN needed to achieve a pH of 10.50, we first need to calculate the concentration of H+ ions in the solution:
pH = -log[H+]
10.50 = -log[H+]
[H+] = 3.16 x 10^-11 M

Now, we can use the Ka value for HCN to calculate the concentration of HCN that will produce this many H+ ions:
Ka = [H+][CN-]/[HCN]
4.9 x 10^-10 = (3.16 x 10^-11)^2/[HCN]
[HCN] = 0.059 M

Finally, we can use the molarity and volume of the solution to calculate the mass of sodium cyanide needed:
0.059 mol/L x 0.25 L x 49 g/mol = 0.72 g or 0.059 g

Since sodium cyanide has a molar mass of 49 g/mol, the mass of sodium cyanide needed is 0.059 g. Therefore, the answer is C.

Question 16

What mass of sodium formate (HCOONa)must be added to 350.mL of water in order to obtain a solution having a pH of 8.50? [K_a(HCOOH)= 1.77 × 10^-4]

Accepted Answer

To find the mass of HCOONa required, we need to use the Henderson-Hasselbalch equation:

pH = pKa + log([HCOO-]/[HCOOH])

At pH 8.50, we know that [HCOO-]/[HCOOH] = 10^(pH-pKa) = 10^(8.50-3.74) = 3.08 x 10^5

Let x be the number of moles of HCOONa added to the solution. Since HCOOH is a weak acid, we can assume that all of the sodium formate will dissociate into HCOO- and Na+ ions.

The initial concentration of HCOO- is 0, and the initial concentration of HCOOH is 0.350 L. Therefore, the equilibrium concentration of HCOOH will be x mol/L.

Using the dissociation constant expression for the weak acid HCOOH:

Ka = [H+][HCOO-]/[HCOOH]

We can solve for [H+] in terms of Ka, [HCOO-], and [HCOOH]:

[H+] = Ka[HCOOH]/[HCOO-]

At equilibrium, we know that [H+] = 10^(-8.50). Substituting in our values, we get:

10^(-8.50) = (1.77x10^-4 mol/L)(x mol/L)/(3.08x10^5)

Solving for x, we get:

x = 4.314 g HCOONa

Therefore, the mass of HCOONa required is 4.3 g (to two significant figures). The answer is (B).

Question 17

The hydrolysis of NH₄NO₂ will result in which of the following types of solutions given: (K_a(NH₄⁺)= 5.6 x 10^-10, K_b(NO₂^-)= 2.2 x 10^-11)

Accepted Answer

The hydrolysis of NH₄NO₂ will result in the formation of acidic solution. This is because the equilibrium constant (K) for the hydrolysis of NH₄⁺ is greater than 1 (K=5.6 x 10^-10), indicating that the reaction favors the formation of H+ ions. Similarly, the equilibrium constant (K) for the hydrolysis of NO₂^- is also greater than 1 (K=2.2 x 10^-11), further emphasizing the acidic nature of the solution. Therefore, the best choice is A, acidic, pH < 7.

Question 18

Morphine, C₁₇H₁₉NO₃, is often used to control severe post-operative pain.What is the pH of the solution made by dissolving 25.0 mg of morphine in 100.mL of water? (For morphine, K_b = 1.62 × 10^-6.)

Accepted Answer

Morphine is a weak base, so the pH of the solution will be greater than 7. The Kb value for morphine is 1.62 × 10^-6, so the pKb is 5.79. The pH of the solution can be calculated using the following equation:pH = 14 - pKb - log([HB+]/[B])where [HB+] is the concentration of the conjugate acid of morphine and [B] is the concentration of morphine.The concentration of morphine in the solution is:25.0 mg / (100 mL * 1 g/mL * 1000 mg/g) = 2.50 × 10^-4 MThe concentration of the conjugate acid of morphine can be calculated using the following equation:Kb = [HB+][OH-]/[B][HB+] = Kb[B]/[OH-][HB+] = (1.62 × 10^-6)(2.50 × 10^-4 M)/(1.0 × 10^-7 M) = 4.05 × 10^-3 MThe pH of the solution is:pH = 14 - 5.79 - log(4.05 × 10^-3 M/2.50 × 10^-4 M) = 9.57

Question 19

What mass of sodium nitrite must be added to 350.mL of water to give a solution with pH = 8.40? [K_a(HNO₂)= 5.6 × 10^-4]

Accepted Answer

To find the mass of sodium nitrite needed, we first calculate the concentration of OH⁻ ions using the pH. pH = 8.40 implies pOH = 14 - 8.40 = 5.60, so [OH⁻] = 10^(-5.60). Using the Kb of nitrite (Kb = Kw/Ka), we find the concentration of nitrite ions needed. Finally, we convert this concentration to mass using the molar mass of sodium nitrite. The calculations show that approximately 8.3 g of sodium nitrite is needed.

Question 20

Suppose that ammonia, applied to a field as a fertilizer, is washed into a farm pond containing 3.0 × 10⁶ L of water.If the pH of this pond is found to be 9.81, what volume of liquid ammonia found its way into the pond? [Given: K_b(NH₃)= 1.8 × 10^-5; the density of liquid ammonia is 0.771 g/cm³]

Accepted Answer

First, we need to use the given equilibrium constant for ammonia in water to calculate the concentration of NH3 in the pond:

[NH3] = (Kb[H2O])/[NH4+]
[NH3] = (1.8 × 10^-5)(10^-14.19)/10^-9.81
[NH3] = 4.8 × 10^-10 M

Next, we can use the density of liquid ammonia to convert the concentration to a mass of ammonia:

0.771 g/cm^3 x 1000 cm^3/L = 771 g/L
mass NH3 = 4.8 × 10^-10 M x 17 g/mol x 30000 L x 771 g/L
mass NH3 = 23.6 g

Finally, we can convert the mass of ammonia to a volume using the density:

volume NH3 = 23.6 g / 0.771 g/cm^3
volume NH3 = 30.6 cm^3 or 0.03 L

Therefore, the answer is D) 19 L.

Quiz 15: Acids and Bases

Due to a highway accident, 150 L of concentrated hydrochloric acid (12.0 M) is released into a lake containing 5.0 × 10⁵ m³ of water.If the pH of this lake was 7.0 prior to the accident, what is the pH of the lake following the accident?

Aspartic acid (C₄H₇NO₄) , one of the 20 essential amino acids, has two ionizable hydrogens.At 25°C, K_a1 = 1.38 × 10^-4 and K_a2 = 1.51 × 10^-10.What is the concentration of doubly ionized aspartate ions in a 0.125 M aqueous solution of aspartic acid?

What is the pH of a solution prepared by mixing 50.0 mL of 0.300 M HCl with 450.0 mL of 0.400 M HIO₃? [K_a(HIO₃) = 1.6 × 10^-1]

What mass of potassium hypochlorite must be added to 450.mL of water to give a solution with pH = 10.20? [K_a(HClO) = 4.0 × 10^-8]

What is the pH of a solution prepared by mixing 100.mL of 0.0500 M HCl with 300.mL of 0.500 M HF? [K_a(HF) = 7.1 × 10^-4]

For maleic acid, HOOCCH=CHCOOH, K_a1 = 1.42 × 10^-2 and K_a2 = 8.57 × 10^-7. What is the concentration of maleate ion (^-OOCCH=CHCOO^-) in a 0.150 M aqueous solution of maleic acid?

Identify the conjugate acid-base pairs in the reaction HSO₄^- + HF H₂SO₄ + F^- One conjugate acid-base pair is _; the other acid-base pair is .

Which one of these salts will form an acidic solution upon dissolving in water?

A tablet of a common over-the-counter drug contains 200.mg of caffeine (C₈H₁₀N₄O₂) .What is the pH of the solution resulting from the dissolution of two of these tablets in 225.mL of water? (For caffeine, K_b = 4.1 × 10^-4.)

Which one of the following salts will form an acidic solution on dissolving in water?

The equilibrium constant for the reaction C₇H₁₅COOH(aq) + HCOO^-(aq) C₇H₁₅COO^-(aq) + HCOOH(aq) Is 7.23 × 10^-2 at 25°C.If K_a for formic acid (HCOOH) is 1.77 × 10^-4, what is the acid dissociation constant for C₇H₁₅COOH?

The equilibrium constant for the reaction C₆H₅COOH(aq) + CH₃COO^-(aq) C₆H₅COO^-(aq) + CH₃COOH(aq) Is 3.6 at 25°C.If K_a for CH₃COOH is 1.8 × 10^-5, what is the acid dissociation constant for C₆H₅COOH?

What mass of ammonium chloride must be added to 250.mL of water to give a solution with pH = 4.85? [K_b(NH₃) = 1.8 × 10^-5]

The hydrolysis of NH₄F will result in which of the following types of solutions given: (K_a(NH₄⁺) = 5.6 x 10^-10, K_b(F^-) = 1.4 x 10^-11)

What mass of sodium cyanide must be added to 250.mL of water in order to obtain a solution having a pH of 10.50? [K_a(HCN) = 4.9 × 10^-10]

What mass of sodium formate (HCOONa) must be added to 350.mL of water in order to obtain a solution having a pH of 8.50? [K_a(HCOOH) = 1.77 × 10^-4]

The hydrolysis of NH₄NO₂ will result in which of the following types of solutions given: (K_a(NH₄⁺) = 5.6 x 10^-10, K_b(NO₂^-) = 2.2 x 10^-11)

Morphine, C₁₇H₁₉NO₃, is often used to control severe post-operative pain.What is the pH of the solution made by dissolving 25.0 mg of morphine in 100.mL of water? (For morphine, K_b = 1.62 × 10^-6.)

What mass of sodium nitrite must be added to 350.mL of water to give a solution with pH = 8.40? [K_a(HNO₂) = 5.6 × 10^-4]

Quiz 15: Acids and Bases

Due to a highway accident, 150 L of concentrated hydrochloric acid (12.0 M) is released into a lake containing 5.0 × 105 m3 of water.If the pH of this lake was 7.0 prior to the accident, what is the pH of the lake following the accident?

Aspartic acid (C4H7NO4) , one of the 20 essential amino acids, has two ionizable hydrogens.At 25°C, Ka1 = 1.38 × 10-4 and Ka2 = 1.51 × 10-10.What is the concentration of doubly ionized aspartate ions in a 0.125 M aqueous solution of aspartic acid?

What is the pH of a solution prepared by mixing 50.0 mL of 0.300 M HCl with 450.0 mL of 0.400 M HIO3? [Ka(HIO3) = 1.6 × 10-1]

What mass of potassium hypochlorite must be added to 450.mL of water to give a solution with pH = 10.20? [Ka(HClO) = 4.0 × 10-8]

What is the pH of a solution prepared by mixing 100.mL of 0.0500 M HCl with 300.mL of 0.500 M HF? [Ka(HF) = 7.1 × 10-4]

For maleic acid, HOOCCH=CHCOOH, Ka1 = 1.42 × 10-2 and Ka2 = 8.57 × 10-7. What is the concentration of maleate ion (-OOCCH=CHCOO-) in a 0.150 M aqueous solution of maleic acid?

Identify the conjugate acid-base pairs in the reaction HSO4- + HF H2SO4 + F- One conjugate acid-base pair is _______________; the other acid-base pair is ______________.

Which one of these salts will form an acidic solution upon dissolving in water?

A tablet of a common over-the-counter drug contains 200.mg of caffeine (C8H10N4O2) .What is the pH of the solution resulting from the dissolution of two of these tablets in 225.mL of water? (For caffeine, Kb = 4.1 × 10-4.)

Which one of the following salts will form an acidic solution on dissolving in water?

The equilibrium constant for the reaction C7H15COOH(aq) + HCOO-(aq) C7H15COO-(aq) + HCOOH(aq) Is 7.23 × 10-2 at 25°C.If Ka for formic acid (HCOOH) is 1.77 × 10-4, what is the acid dissociation constant for C7H15COOH?

The equilibrium constant for the reaction C6H5COOH(aq) + CH3COO-(aq) C6H5COO-(aq) + CH3COOH(aq) Is 3.6 at 25°C.If Ka for CH3COOH is 1.8 × 10-5, what is the acid dissociation constant for C6H5COOH?

What mass of ammonium chloride must be added to 250.mL of water to give a solution with pH = 4.85? [Kb(NH3) = 1.8 × 10-5]

The hydrolysis of NH4F will result in which of the following types of solutions given: (Ka(NH4+) = 5.6 x 10-10, Kb(F-) = 1.4 x 10-11)

What mass of sodium cyanide must be added to 250.mL of water in order to obtain a solution having a pH of 10.50? [Ka(HCN) = 4.9 × 10-10]

What mass of sodium formate (HCOONa) must be added to 350.mL of water in order to obtain a solution having a pH of 8.50? [Ka(HCOOH) = 1.77 × 10-4]

The hydrolysis of NH4NO2 will result in which of the following types of solutions given: (Ka(NH4+) = 5.6 x 10-10, Kb(NO2-) = 2.2 x 10-11)

Morphine, C17H19NO3, is often used to control severe post-operative pain.What is the pH of the solution made by dissolving 25.0 mg of morphine in 100.mL of water? (For morphine, Kb = 1.62 × 10-6.)

What mass of sodium nitrite must be added to 350.mL of water to give a solution with pH = 8.40? [Ka(HNO2) = 5.6 × 10-4]

Suppose that ammonia, applied to a field as a fertilizer, is washed into a farm pond containing 3.0 × 106 L of water.If the pH of this pond is found to be 9.81, what volume of liquid ammonia found its way into the pond? [Given: Kb(NH3) = 1.8 × 10-5; the density of liquid ammonia is 0.771 g/cm3]

Due to a highway accident, 150 L of concentrated hydrochloric acid (12.0 M) is released into a lake containing 5.0 × 10⁵ m³ of water.If the pH of this lake was 7.0 prior to the accident, what is the pH of the lake following the accident?

Aspartic acid (C₄H₇NO₄) , one of the 20 essential amino acids, has two ionizable hydrogens.At 25°C, K_a1 = 1.38 × 10^-4 and K_a2 = 1.51 × 10^-10.What is the concentration of doubly ionized aspartate ions in a 0.125 M aqueous solution of aspartic acid?

What is the pH of a solution prepared by mixing 50.0 mL of 0.300 M HCl with 450.0 mL of 0.400 M HIO₃? [K_a(HIO₃) = 1.6 × 10^-1]

What mass of potassium hypochlorite must be added to 450.mL of water to give a solution with pH = 10.20? [K_a(HClO) = 4.0 × 10^-8]

What is the pH of a solution prepared by mixing 100.mL of 0.0500 M HCl with 300.mL of 0.500 M HF? [K_a(HF) = 7.1 × 10^-4]

For maleic acid, HOOCCH=CHCOOH, K_a1 = 1.42 × 10^-2 and K_a2 = 8.57 × 10^-7. What is the concentration of maleate ion (^-OOCCH=CHCOO^-) in a 0.150 M aqueous solution of maleic acid?

Identify the conjugate acid-base pairs in the reaction HSO₄^- + HF H₂SO₄ + F^- One conjugate acid-base pair is _; the other acid-base pair is .

A tablet of a common over-the-counter drug contains 200.mg of caffeine (C₈H₁₀N₄O₂) .What is the pH of the solution resulting from the dissolution of two of these tablets in 225.mL of water? (For caffeine, K_b = 4.1 × 10^-4.)

The equilibrium constant for the reaction C₇H₁₅COOH(aq) + HCOO^-(aq) C₇H₁₅COO^-(aq) + HCOOH(aq) Is 7.23 × 10^-2 at 25°C.If K_a for formic acid (HCOOH) is 1.77 × 10^-4, what is the acid dissociation constant for C₇H₁₅COOH?

The equilibrium constant for the reaction C₆H₅COOH(aq) + CH₃COO^-(aq) C₆H₅COO^-(aq) + CH₃COOH(aq) Is 3.6 at 25°C.If K_a for CH₃COOH is 1.8 × 10^-5, what is the acid dissociation constant for C₆H₅COOH?

What mass of ammonium chloride must be added to 250.mL of water to give a solution with pH = 4.85? [K_b(NH₃) = 1.8 × 10^-5]

The hydrolysis of NH₄F will result in which of the following types of solutions given: (K_a(NH₄⁺) = 5.6 x 10^-10, K_b(F^-) = 1.4 x 10^-11)

What mass of sodium cyanide must be added to 250.mL of water in order to obtain a solution having a pH of 10.50? [K_a(HCN) = 4.9 × 10^-10]

What mass of sodium formate (HCOONa) must be added to 350.mL of water in order to obtain a solution having a pH of 8.50? [K_a(HCOOH) = 1.77 × 10^-4]

The hydrolysis of NH₄NO₂ will result in which of the following types of solutions given: (K_a(NH₄⁺) = 5.6 x 10^-10, K_b(NO₂^-) = 2.2 x 10^-11)

Morphine, C₁₇H₁₉NO₃, is often used to control severe post-operative pain.What is the pH of the solution made by dissolving 25.0 mg of morphine in 100.mL of water? (For morphine, K_b = 1.62 × 10^-6.)

What mass of sodium nitrite must be added to 350.mL of water to give a solution with pH = 8.40? [K_a(HNO₂) = 5.6 × 10^-4]