Question 1

In a solution labeled "0.0018 M barium hydroxide" what is the molarity of OH^-?

Accepted Answer

Barium hydroxide is Ba(OH)2, which dissociates into one Ba2+ ion and two OH- ions. Therefore, a 0.0018 M solution of barium hydroxide will have a molarity of OH- ions that is double that, or 0.0036 M.

Question 2

The pH of 0.010 M H₃PO₄(aq)is 2.24; estimate the concentration of PO₄³^- in the solution.For H₃PO₄,the values of K_a1,K_a2,and K_a3 are 7.6 *10^-³,6.2 * 10^-⁸,and 2.1 * 10^-13,respectively.

Accepted Answer

The concentration of PO₄³⁻ is determined by the third dissociation step of H₃PO₄, which is very weak (Kₐ₃ = 2.1 × 10⁻¹³). Given the pH, the concentration of H⁺ is 5.75 × 10⁻³ M, and the concentration of PO₄³⁻ is very low, approximately 2.3 × 10⁻¹⁸ M.

Question 3

Calculate the equilibrium constant for the reaction S^2-(aq)+ H₂O(l)↔ HS^-(aq)+ OH^-(aq), Given K_a1 = 1.3 * 10^-7 and K_a2 = 7.1 * 10^-15 for H₂S.

Accepted Answer

The answer of Calculate the equilibrium constant for the reaction...

Question 4

If $\alpha$(HSO₃^-)= 0.83 at pH 2.5,what are $\alpha$(H₂SO₃)and $\alpha$(SO₃²^-)at this pH? For H₂SO₃,pK_a1 and pK_a2 are 1.81 and 6.91,respectively.

Accepted Answer

The answer of If $\alpha$(HSO₃^-)= 0.83 at pH 2.5,what are...

Question 5

The amino acid alanine,HOOC-CH(CH₃)NH₃⁺,has K_a1 = 4.5 * 10^-3 and K_a2 = 1.4 * 10^-10.Calculate $\alpha$(^-OOC-CH(CH₃)NH₃⁺)at pH 3.

Accepted Answer

We can use the Henderson-Hasselbalch equation to calculate the ratio F1F1F1S1F1F1F10(F1F1F1S1^F1F1F10OOC-CH(CH₃)NH₃⁺) at pH 3: pH = pKa + log([A-]/[HA]) where pKa is the acid dissociation constant of the carboxyl group in alanine (approximately 2.34), [A-] is the concentration of alanine in its deprotonated form (with a negative charge on the carboxyl group), and [HA] is the concentration of alanine in its protonated form (with no charge on the carboxyl group). At pH 3, we can assume that most of the alanine molecules will be protonated, so [HA] ≈ total concentration of alanine. We can also assume that the concentration of hydroxide ions (OH-) is negligible compared to the concentration of hydrogen ions (H+), so [A-] ≈ 0. Therefore, we can simplify the Henderson-Hasselbalch equation to: pH = pKa + log(0/[HA]) which gives us: [HA] = 10^(pKa - pH) = 10^(2.34 - 3) = 0.468 Now we can use the equation for the fractional saturation of alanine: F1F1F1S1F1F1F10(F1F1F1S1^F1F1F10OOC-CH(CH₃)NH₃⁺) = [_a1]/([_a1] + K_a1) + [_a2]/([_a2] + K_a2) where [_a1] and [_a2] are the concentrations of alanine in its protonated form and deprotonated form, respectively. Using the values given in the problem, we get: F1F1F1S1F1F1F10(F1F1F1S1^F1F1F10OOC-CH(CH₃)NH₃⁺) = [0.468]/([0.468] + 4.5∙10^-10) + [1]/([1] + 1.4∙10^-10) ≈ 0.823 Therefore, the answer is B, 0.82.

Question 6

The fractional composition diagram for the amino acid alanine is given below.  Write the structure of the dominant species at pH 1,6,and 12,respectively.

Accepted Answer

The answer of The fractional composition diagram for the amino...

Question 7

The pH of 0.010 M H₃PO₄(aq)is 2.24.Estimate the concentration of HPO₄²^- in the solution.For H₃PO₄,the values of K_a1,K_a2,and K_a3 are 7.6 * 10^-3,6.2 * 10^-⁸,and 2.1 *10^-13,respectively.

Accepted Answer

The concentration of HPO₄²⁻ is determined by the second dissociation constant, Kₐ₂, which is 6.2 * 10⁻⁸ M.

Question 8

Estimate the pH of 0.10 M Na₂HPO₄(aq)given pK_a1 = 2.12,pK_a2 = 7.21,and pK_a3 = 12.68 for phosphoric acid.

Accepted Answer

NaS1U1B12S1U1B0 dissociates in water to produce S1U1B12S1U1B0- and Na+ ions. The S1U1B12S1U1B0- ion is a conjugate base of H3S1U1B14S1U1B0, which is a triprotic acid. Therefore, the S1U1B12S1U1B0- ion can react with water to produce H3S1U1B14S1U1B0, which can then donate protons to water, producing H3O+ ions.

The pH of a 0.10 M solution of NaS1U1B12S1U1B0 is dependent on the equilibrium concentrations of H3S1U1B14S1U1B0 and its conjugate bases, H2S1U1B1PO4- and H1S1U1B2PO4^2-. Using the given pKS1U1B1a values for H3S1U1B14S1U1B0, we can calculate the equilibrium concentrations of each species using an ICE table.

The first dissociation:
H3S1U1B14S1U1B0 + H2O ⇌ H2S1U1B1PO4- + H3O+

Initial: 0.10 M              0                0
Change: -x                +x            +x
Equilibrium: 0.10 - x   x              x

Using the equilibrium concentrations, we can calculate the pH of the solution:

pH = -log[H3O+]
[H3O+] = x = 6.29 × 10^-9
pH = 8.20

Therefore, the best choice is B) 9.94, which is the closest option to 8.20.

Question 9

The amino acid alanine,HOOC-CH(CH₃)NH₃⁺,has K_a1 = 4.5 * 10^-3 and K_a2 = 1.4 * 10^-10.Calculate $\alpha$(HOOC-CH(CH₃)NH₃⁺)at pH 3.

Accepted Answer

The answer of The amino acid alanine,HOOC-CH(CH₃)NH₃⁺,has K_a1 = 4.5...

Question 10

All of the following are Lewis bases except

Accepted Answer

Lewis bases are species that donate a pair of electrons. C, SO3, is a Lewis acid because it accepts electron pairs, not donates them.

Question 11

the pH of 0.10 M and 0.40 M NaHCO₃(aq)solutions is 8.31 for both?

Accepted Answer

NaHCO3 is a weak base, and when it dissolves in water, it forms HCO3- (bicarbonate) ions and Na+ ions. The pH of the resulting solution will depend on the concentration of HCO3- ions. However, at a concentration of 0.10 M or 0.40 M, the concentration of HCO3- ions is not high enough to significantly affect the pH of the solution. Therefore, the pH of both solutions is approximately equal to the pKa of HCO3- (6.35), which is 8.31 at room temperature. Since the concentration of Na+ ions is the same in both solutions, the pH is also the same.

Question 12

If $\alpha$(HSO₃^-)= 0.45 at pH 7.0,what are $\alpha$(H₂SO₃)and $\alpha$(SO₃²^-)at this pH? For H₂SO₃,pK_a1 and pK_a2 are 1.81 and 6.91,respectively.

Accepted Answer

The answer of If $\alpha$(HSO₃^-)= 0.45 at pH 7.0,what are...

Question 13

Of the following,which is not a Lewis acid?

Accepted Answer

All of the other options contain atoms that can accept electron pairs and therefore function as Lewis acids. However, option A contains only atoms that do not have empty orbitals to accept electron pairs and therefore cannot function as Lewis acids.

Question 14

The amino acid methionine,HOOC-CH(CH₂CH₂SCH₃)NH₃⁺,has pK_a1 = 2.2 and pK_a2 = 9.1.If this amino acid is represented by H₂L⁺,the major species at pH 6 is

Accepted Answer

At pH 6, the amino acid is protonated and exists as the species HL. This is because at pH 6 (which is below the pKa of the amino group), the amino group will be protonated and positively charged (NH3+), while the carboxyl group will remain deprotonated and negatively charged (COO-). Therefore, the amino acid will exist in its protonated form, which is HL. The other options involve species that would result from deprotonation of the amino group or protonation of the carboxyl group, which are not relevant at this pH.

Question 15

The amino acid alanine,HOOC-CH(CH₃)NH₃⁺,has K_a1 = 4.5 * 10^-3 and K_a2 = 1.4 * 10^-10.Calculate $\alpha$(^-OOC-CH(CH₃)NH₃⁺)at pH 10.

Accepted Answer

The correct answer is A because at pH 10, the amino acid is predominantly in the form of $\alpha$(^-OOC-CH(CH₃)NH₃⁺).

Question 16

For a solution of phosphoric acid,write the equation for $\alpha$(HPO₄²^-).

Accepted Answer

The expression for $\alpha$(HPO$_4$ $^{2-}$) is derived from the fraction of the total concentration of phosphoric acid species that is in the form of HPO$_4$ $^{2-}$. This is given by the product of the first two dissociation constants $K_{a1}$ and $K_{a2}$ multiplied by the concentration of hydronium ions $[H_3O^+]$, divided by the sum of all species concentrations, which is represented by the denominator.

Question 17

The boxes below contain a series of 0.1 M aqueous solutions of increasing pH where A is the solution of lowest pH and E is the solution of highest pH. Match each box with the correct compound. phenol,pK_a = 9.89 cyanide ion,pK_b = 4.69 pyridine,pK_b = 8.75 hydrogen sulfate ion,pK_a = 1.92 sodium nitrate

Accepted Answer

The answer of The boxes below contain a series of...

Question 18

The fractional composition diagram for the amino acid alanine is shown below.  What do the two points represent where alpha is 0.5?

Accepted Answer

The answer of The fractional composition diagram for the amino...

Question 19

Both H₂O and OH^- can act as a Brønsted acid and a Brønsted base but not as a Lewis acid.

Accepted Answer

Both H₂O and OHF1F1F1S1^-F1F1F10 can donate and accept protons and thus act as a Brønsted acid and a Brønsted base. However, neither of them has an empty orbital to accept a pair of electrons and act as a Lewis acid. Therefore, option A is true.

Question 20

All of the following acids have the same strength in water except

Accepted Answer

HF (hydrofluoric acid) differs in strength from the other acids listed. HNO3, HClO4, and HBr are all considered strong acids, meaning they completely dissociate in water. HF, however, is a weak acid because it does not fully dissociate in water.

Quiz 12: Acids and Bases

In a solution labeled "0.0018 M barium hydroxide" what is the molarity of OH^-?

The pH of 0.010 M H₃PO₄(aq) is 2.24; estimate the concentration of PO₄³^- in the solution.For H₃PO₄,the values of K_a1,K_a2,and K_a3 are 7.6 10^-³,6.2 10^-⁸,and 2.1 * 10^-13,respectively.

Calculate the equilibrium constant for the reaction S^2-(aq) + H₂O(l) ↔ HS^-(aq) + OH^-(aq) , Given K_a1 = 1.3 * 10^-7 and K_a2 = 7.1 * 10^-15 for H₂S.

If $\alpha$ (HSO₃^-) = 0.83 at pH 2.5,what are $\alpha$ (H₂SO₃) and $\alpha$ (SO₃²^-) at this pH? For H₂SO₃,pK_a1 and pK_a2 are 1.81 and 6.91,respectively.

The amino acid alanine,HOOC-CH(CH₃) NH₃⁺,has K_a1 = 4.5 * 10^-3 and K_a2 = 1.4 * 10^-10.Calculate $\alpha$ (^-OOC-CH(CH₃) NH₃⁺) at pH 3.

The pH of 0.010 M H₃PO₄(aq) is 2.24.Estimate the concentration of HPO₄²^- in the solution.For H₃PO₄,the values of K_a1,K_a2,and K_a3 are 7.6 * 10^-3,6.2 * 10^-⁸,and 2.1 *10^-13,respectively.

Estimate the pH of 0.10 M Na₂HPO₄(aq) given pK_a1 = 2.12,pK_a2 = 7.21,and pK_a3 = 12.68 for phosphoric acid.

The amino acid alanine,HOOC-CH(CH₃) NH₃⁺,has K_a1 = 4.5 * 10^-3 and K_a2 = 1.4 * 10^-10.Calculate $\alpha$ (HOOC-CH(CH₃) NH₃⁺) at pH 3.

All of the following are Lewis bases except

the pH of 0.10 M and 0.40 M NaHCO₃(aq)solutions is 8.31 for both?

If $\alpha$ (HSO₃^-) = 0.45 at pH 7.0,what are $\alpha$ (H₂SO₃) and $\alpha$ (SO₃²^-) at this pH? For H₂SO₃,pK_a1 and pK_a2 are 1.81 and 6.91,respectively.

Of the following,which is not a Lewis acid?

The amino acid methionine,HOOC-CH(CH₂CH₂SCH₃) NH₃⁺,has pK_a1 = 2.2 and pK_a2 = 9.1.If this amino acid is represented by H₂L⁺,the major species at pH 6 is

The amino acid alanine,HOOC-CH(CH₃) NH₃⁺,has K_a1 = 4.5 * 10^-3 and K_a2 = 1.4 * 10^-10.Calculate $\alpha$ (^-OOC-CH(CH₃) NH₃⁺) at pH 10.

For a solution of phosphoric acid,write the equation for $\alpha$ (HPO₄²^-) .

The fractional composition diagram for the amino acid alanine is shown below. $The fractional composition diagram for the amino acid alanine is shown below. What do the two points represent where alpha is 0.5?$ What do the two points represent where alpha is 0.5?

Both H₂O and OH^- can act as a Brønsted acid and a Brønsted base but not as a Lewis acid.

All of the following acids have the same strength in water except

Quiz 12: Acids and Bases

In a solution labeled "0.0018 M barium hydroxide" what is the molarity of OH-?

The pH of 0.010 M H3PO4(aq) is 2.24; estimate the concentration of PO43- in the solution.For H3PO4,the values of Ka1,Ka2,and Ka3 are 7.6 *10-3,6.2 * 10-8,and 2.1 * 10-13,respectively.

Calculate the equilibrium constant for the reaction S2-(aq) + H2O(l) ↔ HS-(aq) + OH-(aq) , Given Ka1 = 1.3 * 10-7 and Ka2 = 7.1 * 10-15 for H2S.

If α\alphaα (HSO3-) = 0.83 at pH 2.5,what are α\alphaα (H2SO3) and α\alphaα (SO32-) at this pH? For H2SO3,pKa1 and pKa2 are 1.81 and 6.91,respectively.

The amino acid alanine,HOOC-CH(CH3) NH3+,has Ka1 = 4.5 * 10-3 and Ka2 = 1.4 * 10-10.Calculate α\alphaα (-OOC-CH(CH3) NH3+) at pH 3.

The fractional composition diagram for the amino acid alanine is given below. Write the structure of the dominant species at pH 1,6,and 12,respectively.

The pH of 0.010 M H3PO4(aq) is 2.24.Estimate the concentration of HPO42- in the solution.For H3PO4,the values of Ka1,Ka2,and Ka3 are 7.6 * 10-3,6.2 * 10-8,and 2.1 *10-13,respectively.

Estimate the pH of 0.10 M Na2HPO4(aq) given pKa1 = 2.12,pKa2 = 7.21,and pKa3 = 12.68 for phosphoric acid.

The amino acid alanine,HOOC-CH(CH3) NH3+,has Ka1 = 4.5 * 10-3 and Ka2 = 1.4 * 10-10.Calculate α\alphaα (HOOC-CH(CH3) NH3+) at pH 3.

All of the following are Lewis bases except

the pH of 0.10 M and 0.40 M NaHCO3(aq)solutions is 8.31 for both?

If α\alphaα (HSO3-) = 0.45 at pH 7.0,what are α\alphaα (H2SO3) and α\alphaα (SO32-) at this pH? For H2SO3,pKa1 and pKa2 are 1.81 and 6.91,respectively.

Of the following,which is not a Lewis acid?

The amino acid methionine,HOOC-CH(CH2CH2SCH3) NH3+,has pKa1 = 2.2 and pKa2 = 9.1.If this amino acid is represented by H2L+,the major species at pH 6 is

The amino acid alanine,HOOC-CH(CH3) NH3+,has Ka1 = 4.5 * 10-3 and Ka2 = 1.4 * 10-10.Calculate α\alphaα (-OOC-CH(CH3) NH3+) at pH 10.

For a solution of phosphoric acid,write the equation for α\alphaα (HPO42-) .

The fractional composition diagram for the amino acid alanine is shown below. What do the two points represent where alpha is 0.5?

Both H2O and OH- can act as a Brønsted acid and a Brønsted base but not as a Lewis acid.

All of the following acids have the same strength in water except

In a solution labeled "0.0018 M barium hydroxide" what is the molarity of OH^-?

The pH of 0.010 M H₃PO₄(aq) is 2.24; estimate the concentration of PO₄³^- in the solution.For H₃PO₄,the values of K_a1,K_a2,and K_a3 are 7.6 10^-³,6.2 10^-⁸,and 2.1 * 10^-13,respectively.

Calculate the equilibrium constant for the reaction S^2-(aq) + H₂O(l) ↔ HS^-(aq) + OH^-(aq) , Given K_a1 = 1.3 * 10^-7 and K_a2 = 7.1 * 10^-15 for H₂S.

If $\alpha$ (HSO₃^-) = 0.83 at pH 2.5,what are $\alpha$ (H₂SO₃) and $\alpha$ (SO₃²^-) at this pH? For H₂SO₃,pK_a1 and pK_a2 are 1.81 and 6.91,respectively.

The amino acid alanine,HOOC-CH(CH₃) NH₃⁺,has K_a1 = 4.5 * 10^-3 and K_a2 = 1.4 * 10^-10.Calculate $\alpha$ (^-OOC-CH(CH₃) NH₃⁺) at pH 3.

The pH of 0.010 M H₃PO₄(aq) is 2.24.Estimate the concentration of HPO₄²^- in the solution.For H₃PO₄,the values of K_a1,K_a2,and K_a3 are 7.6 * 10^-3,6.2 * 10^-⁸,and 2.1 *10^-13,respectively.

Estimate the pH of 0.10 M Na₂HPO₄(aq) given pK_a1 = 2.12,pK_a2 = 7.21,and pK_a3 = 12.68 for phosphoric acid.

The amino acid alanine,HOOC-CH(CH₃) NH₃⁺,has K_a1 = 4.5 * 10^-3 and K_a2 = 1.4 * 10^-10.Calculate $\alpha$ (HOOC-CH(CH₃) NH₃⁺) at pH 3.

the pH of 0.10 M and 0.40 M NaHCO₃(aq)solutions is 8.31 for both?

If $\alpha$ (HSO₃^-) = 0.45 at pH 7.0,what are $\alpha$ (H₂SO₃) and $\alpha$ (SO₃²^-) at this pH? For H₂SO₃,pK_a1 and pK_a2 are 1.81 and 6.91,respectively.

The amino acid methionine,HOOC-CH(CH₂CH₂SCH₃) NH₃⁺,has pK_a1 = 2.2 and pK_a2 = 9.1.If this amino acid is represented by H₂L⁺,the major species at pH 6 is

The amino acid alanine,HOOC-CH(CH₃) NH₃⁺,has K_a1 = 4.5 * 10^-3 and K_a2 = 1.4 * 10^-10.Calculate $\alpha$ (^-OOC-CH(CH₃) NH₃⁺) at pH 10.

For a solution of phosphoric acid,write the equation for $\alpha$ (HPO₄²^-) .

The fractional composition diagram for the amino acid alanine is shown below. $The fractional composition diagram for the amino acid alanine is shown below. What do the two points represent where alpha is 0.5?$ What do the two points represent where alpha is 0.5?

Both H₂O and OH^- can act as a Brønsted acid and a Brønsted base but not as a Lewis acid.