Chem2 exam 3

10.87

A 20.00-mL sample of 0.3000 M HBr is titrated with 0.15 M NaOH. What is the pH of the solution after 40.3 mL of NaOH have been added to the acid?

.85

A 50.0-mL sample of 0.50 M HCl is titrated with 0.50 M NaOH. What is the pH of the solution after 28.0 mL of NaOH have been added to the acid?

0.025 mol HCl

A buffer is prepared by adding 150 mL of 1.0 M NaOH to 250 mL of 1.0 M NaH2PO4. How many moles of HCl must be added to this buffer solution to change the pH by 0.18 units?

4.92

A buffer is prepared by adding 300.0 mL of 2.0 M NaOH to 500.0 mL of 2.0 M CH3COOH. What is the pH of this buffer? [Ka(CH3COOH) = 1.8 × 10-5]

0.30 M CH3COONa

A buffer is to be prepared by adding solid sodium acetate to 0.10 M CH3COOH. Which of the following concentrations of sodium acetate will produce the most effective buffer?

soln is neutral

A solution is prepared by adding 0.10 mol of lithium nitrate, LiNO3, to 1.00 L of water. Which statement about the solution is correct?

soln is neutral

A solution is prepared by adding 0.10 mol of potassium chloride, KCl, to 1.00 L of water. Which statement about the solution is correct?

the solution is neutral.

A solution is prepared by adding 0.10 mol of potassium chloride, KCl, to 1.00 L of water. Which statement about the solution is correct? the solution is acidic. the solution is basic. the values for Ka and Kb for the species in solution must be known before a prediction can be made. the solution is a strong oxidant. the solution is neutral.

The solution is basic.

A solution is prepared by adding 0.10 mol of sodium sulfide, Na2S, to 1.00 L of water. Which statement about the solution is correct?

It is a buffer, pH = pKa of formic acid.

A solution is prepared by adding 100 mL of 0.2 M hydrochloric acid to 100 mL of 0.4 M sodium formate. Is this a buffer solution, and if so, what is its pH?

adding a small amount of dilute hydrochloric acid

An acetate buffer has a pH of 4.40. Which of the following changes will cause the pH to decrease?

4.71

An acetic acid buffer containing 0.50 M CH3COOH and 0.50 M CH3COONa has a pH of 4.74. What will the pH be after 0.0020 mol of HCl has been added to 100.0 mL of the buffer?

The values for Ka and Kb for the species in solution must be known before a prediction can be made.

An aqueous solution is prepared by dissolving the salt formed by the neutralization of a weak acid by a weak base. Which statement about the solution is correct? The values for Ka and Kb for the species in solution must be known before a prediction can be made. The solution is strongly basic. The solution is neutral. The solution is weakly basic. The solution is acidic.

5.6 × 10-8 M

Arsenic acid, H3AsO4, is used industrially to manufacture insecticides. Arsenic acid is a polyprotic acid with K1 = 2.5 × 10-4, K2 = 5.6 × 10-8, and K3 = 3 × 10-13. What is the concentration of the HAsO42- in a solution whose initial arsenic acid concentration was 0.35 M?

2.02

Arsenic acid, H3AsO4, is used industrially to manufacture insecticides. Arsenic acid is a polyprotic acid with Ka1 = 2.5 × 10-4, Ka2 = 5.6 × 10-8, and Ka3 = 3 × 10-13. What is the pH of a solution whose initial arsenic acid concentration was 0.36 M?

2.0 × 10-6 M

Calculate the concentration of malonate ion (C3H2O42-) in a 0.200 M solution of malonic acid (C3H4O4). (For malonic acid, Ka1 = 1.4 × 10-3, Ka2 = 2.0 × 10-6.)

3.97

Calculate the pH of a buffer solution that contains 0.25 M benzoic acid (C6H5CO2H) and 0.15 M sodium benzoate (C6H5COONa). (Ka = 6.5 × 10-5 for benzoic acid)

0.10 mol L-1 HCl and 0.15 mol L-1 NH3

Equal volumes of the following pairs of solutions are mixed. Which pair will produce a buffer solution?

strongly basic

For H3PO4, Ka1 = 7.3 × 10-3, Ka2 = 6.2 × 10-8, and Ka3 = 4.8 × 10-13. A 0.10 M aqueous solution of Na3PO4 therefore would be

acidic

For H3PO4, Ka1 = 7.3 × 10-3, Ka2 = 6.2 × 10-8, and Ka3 = 4.8 × 10-13. A 0.10 M aqueous solution of NaH2PO4 therefore would be

A.HCO3−/H2CO3

Select the pair that consists of a base and its conjugate acid in that order. A.HCO3−/H2CO3 ● B.NH4+/NH3 ● C.HCO3−/CO32− ● D.CO32− /CO22− ● E.H3PO4/ HPO42−

CO32− and OH−

Select the two Brønsted-Lowry bases in the following equation:CO32−(aq) + H2O(l) ⇌ HCO3−(aq) + OH−(aq)

T

T/F Amphoteric oxides exhibit both acidic and basic properties.

F

T/F In aqueous solutions at 25°C, the sum of the hydroxide ion and hydronium ion concentrations ([H3O+] + [OH -]) equals 1 × 10-14.

H3PO4

The conjugate acid of H2PO4− is: HPO42− PO43− H2PO3− H3PO4 H3PO3

H2CO3

The conjugate acid of HCO3− is:

HPO42−

The conjugate base of H2PO4− is:

CO2-3

The conjugate base of HCO3- is:

4.5-6.5

The indicator propyl red has Ka = 3.3 × 10-6. What would be the approximate pH range over which it would change color?

NH4+

What is the conjugate acid of NH3?

HC2H3O2 AKA CH3COOH acetic acid

What is the conjugate acid of the acetate ion?

H2O

What is the conjugate acid of the hydroxide ion?

NH2-

What is the conjugate base of NH3? NH4 NH4+ NH2 NH2+ NH2-

HSO4-

What is the conjugate base of sulfuric acid?

amphoteric

What is the name given to a substance that can act as a Brønsted acid or as a Brønsted base according to what it is reacting with?

brønsted base

What is the name of a proton acceptor in an acid-base reaction? brønsted acid brønsted base lewis base arrhenius acid arrhenius base

brønsted acid

What is the name of a proton donor in an acid-base reaction? brønsted acid arrhenius acid lewis base arrhenius base brønsted base

7

What is the pH at the equivalence point in the titration of 100 mL of 0.10 M HCl with 0.10 M NaOH?

4.30

What is the pH of a buffer solution prepared by dissolving 0.20 mole of cyanic acid (HCNO) and 0.80 mole of sodium cyanate (NaCNO) in enough water to make 1.0 liter of solution?[Ka(HCNO) = 2.0 × 10-4]4.30

7.19

What is the pH of a solution prepared by mixing 500.mL of 0.10 M NaOCl and 500. mL of 0.20 M HOCl?[Ka(HOCl) = 3.2 × 10-8]

NH4+(aq) and OH−(aq)

When ammonia, NH3, is dissolved in water, which ions are formed?

between 0 and 7

Which best describes the pH at the equivalence point of a titration of a weak base with a strong acid?

a polyprotic acid has more than two ionizable protons.

Which is the correct statement? NH3 is a diprotic acid. a polyprotic acid has more than two ionizable protons. all protons are lost from a polyprotic acid at the same time. NH3 is a polyprotic acid. H2O is a diprotic acid.

NaH2PO4 and Na2HPO4

Which may be used to prepare a buffer having a pH of 8.8?Ka= 7 × 10-3 for H3PO4; 8 × 10-8 for H2PO4-; 5 × 10-13 for HPO42-

It would taste sour.

Which of the following is not an attribute of a base? It has the ability to neutralize acids. It provides OH− ions in aqueous solution. It would taste sour. It is an electrolyte. It reacts with some organic dyes to cause them to change color.

It is a nonelectrolyte.

Which of the following is not an attribute of an acid? It is a nonelectrolyte. It reacts with some organic dyes to cause them to change color. It tastes sour. It provides H+ ions in aqueous solution. It reacts with active metals.

Kw = [OH-][H3O+]

Which of the following is the correct equilibrium expression for the autoionization of water?

KNO3

Which one of the following substances will give an aqueous solution of pH closest to 7? KNO3 CO2 CH3NH2 NH3 NH4I

NH4Br

Which one of these salts will form an acidic solution upon dissolving in water? NH4Br LiBr NaCN KOH NaF

HNO3 and NaNO3

Which pair of substances cannot form a buffered aqueous solution? HNO2 and NaNO2 NH3 and (NH4)2SO4 HCN and KCN HF and NaF HNO3 and NaNO3

H3PO4, NaH2PO4

Which pair of substances could form a buffered aqueous solution? HNO3, NaNO3 H3PO4, NaH2PO4 H2SO4, CH3COOH HCl, NaCl NH3, NaOH

a solution containing a weak acid and its conjugate base

Which results in a buffered solution? a solution containing two organic liquids a solution containing a catalyst a solution containing a strong base and its conjugate acid a solution containing a weak acid and its conjugate base a solution containing a strong acid and its conjugate base

5.07

You have 500.0 mL of a buffer solution containing 0.20M acetic acid (CH3COOH) and 0.30 M sodium acetate (CH3COONa). What will the pH of this solution be after the addition of 20.0 mL of 1.00 M NaOH solution? [Ka(CH3COOH) = 1.8 × 10-5]

false. only strong arrhenius bases contain hydroxide ions

t/f All Brønsted-Lowry bases contain the hydroxide ion, OH-.

true. for a BL base to receive a proton, it must have a loan pair

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

true

t/f Hydrated metal ions in aqueous solution can act as Brønsted-Lowry acids.

false. a BL ACID must contain a proton

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

false

t/f The first ionization constant Ka1 is always smaller than the second ionization constant Ka2 for the ionization of a diprotic acid.