Test 4 Review

Acid/Bases

100

What of the following is NOT a conjugate acid-base pair?

a. H₃O⁺ / H₂O

b.  HPO₄^- / H₂PO₄^-  

c. HC₂H₃O₂ / C₂H₃O₂^-

d. NH₃ / NH₄⁺

e. All of the above are conjugate acid-base pairs.

e

200

Which of the following solutions would have the lowest pH? Assume they are all 0.5M in acid at 25^oC. Acid is followed by Ka value.

a. HClO₂, 1.1x10^-2

b. HNO₂, 4.6x10^-4

c. HCN, 4.9x10^-10

d. HCHO₂, 1.8x10^-4

a

300

Calculate the hydronium ion concentration in aqueous solution with a pH of 10.56.

2.75x10^-11M

400

Chloric acid is a strong acid. Determine the pOH of a 0.0115M HClO₃ solution.

12.06

500

Calculate the pH, pOH and H₃O⁺ concentration of a solution that contains 4.25x10^-5M OH^- at 25^oC. Identify the solution as acidic, basic, or neutral.

[H₃O⁺]=2.35x10^-10M

pH = 9.63

pOH=4.37

basic

Weak Acids/Bases & Buffers

100

Determine the K_b of ClO^- at 25^oC. The K_a of HClO is 2.9x10^-8. 

3.45x10^-7

200

Determine the [H₃O⁺] in a 0.315M HCN solution. The K_a of HCN is 4.9x10^-10.

1.24x10^-5M

300

Calculate the pH of a buffer that is 0.065M in NaNO₂ and 0.040M in HNO₂. The K_a for HNO₂ is 4.50x10^-4.

3.56

400

Calculate the pOH in a 0.65 M solution of NaOCl. The K_a of HOCl 2.8x10^-8_.

3.32

500

What is the pH and hydroxide concentration of a 0.35M solution of sodium nitrate, NaNO₂? the pK_a for nitrous acid, HNO₂, is 3.35?

[OH^-] = 2.8x10^-6

pH = 8.45

Titration and Solubility

100

A titration of a weak acid-strong base will have an equivalence point of what?

 greater than 7.

200

BaF₂ is placed in water. If it has a K_sp 2.45x10^-5, what will be the concentrations of each ion?

[Ba²⁺] = 1.83x10^-2M

[F-] = 3.66x10^-2M

300

What volume of 0.60M NaOH is needed to neutralize a 15.00mL sample of 0.80M HCl?

0.020L or 20mL

400

The K_sp of BaSO₄ is 1.1 x 10^-10. What is the molar solubility of BaSO₄ in 0.050M Na₂SO₄?

2.2x10^-9M

500

25.0mL of HNO₃ was used to titrate 13.45mL of 0.200M Sr(OH)₂ to the equivalence point. What was the concentration of the HNO₃?

0.215M

Electro-chemistry

100

An electrochemical cell is designed using silver as one electrode and another metal lower than silver on the table provided. The cell potential is +1.14V. The potential for the unknown half-reaction is _____ and that electrode is the __________.

-0.34V; anode

200

Write the balanced overall reaction for aluminum reacting with copper(II) ion and how many electrons are transferred. 

6e^-

300

Consider the cell reaction Zn(s) + 2Ag⁺(aq) --> Zn²⁺(aq)+2Ag(s). Calculate the value of ΔG^o and K for this cell. 

ΔG^o=301kJ/mol

K=5.41x10⁵²

400

Calculate the cell potential for the following reaction that takes place in an electrochemical cell at 25^oC. Spontaneous or non-spontaneous?

Pb(s)|Pb²⁺(aq)(2.21M)||Au⁺(aq)(0.475M)|Au(s)

+1.79

500

Pb|Pb²⁺(aq)||Ag⁺(aq)|Ag(s)

Using the cell notation above calculate the standard cell potential, the ΔG^o and the K for the reaction occurring at 25^oC. 

0.93V

-179kJ/mol

2.77x10³¹

Random

100

What equations do we have to remember about ΔG^o of the cell and E^o_cell.

ΔG^o= nFE^o_cell

E^o_cell = cathode-anode

200

Which of the following is a polyprotic acid?

a. C₂H₅OH

b. CH₄

c. HF

d.OH^-

e. HCN

a

300

Which of the following salts when dissolved in water, produces the solution with the lowest pH and why?

a. NaI

b. NaF

c. NaCl

d. NaBr

e. Cannot be determined

b.

400

Identify the following as a Lewis acid/base or neither.

a. H₂O

b. BF₃

c. AlCl₃

d. NH₃

e. NaCl

a. lewis base

b. lewis acid

c. lewis acid

d. lewis base

e. neither/salt

500

Which statement is not correct?

a. A battery is an example of an electrochemical cell.

b. Oxidation occurs at the anode.

c. Chemical species can have their oxidation number increased at the cathode.

d. Elemental metal is routinely converted to metal cations at the anode.

c.