Chem 102 - General Chemistry » Winter 2022 » Exam 3
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Question #1
Which one of the following, A–D, is correct?
A.
NaHSO3 is a stronger base than NaHSO4.
B.
K2SO3 is a weaker base than KHSO3.
C.
K2CO3 is a weaker base than KHCO3.
D.
Na2HPO4 is a stronger acid than NaH2PO4.
Question #2
A BrØnsted-Lowry base is defined as a substance that __________.
A.
acts as a proton acceptor
B.
acts as a proton donor
C.
increases [OH-] when placed in H2O
D.
decreases [H+] when placed in H2O
E.
increases Ka when placed in H2O
Question #3
The acid-dissociation constants of phosphorous acid (H3PO3) are Ka1 = 7.5 × 10-3, Ka2 = 6.2 × 10-8, and Ka3 = 4.2 × 10-13 at 25.0°C. Which dissociation constants would you use to solve for the pH of 0.5M solution of Na3PO3?
A.
Kb2 and Ka3
B.
Kb1 and Ka2
C.
Kb3
D.
Kb3 and Ka1
E.
Kb3 and Ka2
F.
Ka1
Question #4
If the pOH of an aqueous H2SO4 solution is 12 What would be the concentration of H2SO4 ?
A.
0.05
B.
0.015
C.
0.005
D.
0.008
Question #5
If the pOH of an aqueous H2SO4 solution is 12 Would the pOH of solution in part A increase, decrease or remain the same if the water evaporates on a hot day
A.
remain the same if the water evaporates on a hot day
B.
decrease
C.
increase
Question #6
Arrange the following 0.10 M aqueous solutions in order of increasing pH (Low pH to high pH): NaOH, HBr, NaCH3CO2, KBr, NH4Br.
A.
HBr, NH4Br, KBr, NaCH3CO2, NaOH
B.
HBr, KBr, NH4Br, NaCH3CO2, NaOH
C.
NaOH, NaCH3CO2, NH4Br, KBr, HBr
D.
NaOH, NaCH3CO2, KBr, NH4Br, HBr
Question #7
The conjugate acid of H2PO4 - is __________
A.
H3O+
B.
H2PO4
C.
H3PO4
D.
HPO4-2
E.
none of the above
Question #8
What is the pH of your best liquid soap made from a fatty acid (HA) that has a pKa value of 4.0? The concentration of the active ingredient for the solution, a fatty acid conjugate base (NaA), is 0.23 M NaA.
A.
8.08
B.
5.48
C.
6.78
D.
8.68
E.
9.23
Question #9
Which of the following acids has the weakest conjugate base? 0.1 M HBO, pKa = 2.43 0.1 M HA, pKa = 4.55 0.1 M HMO, pKa = 8.23 0.1 M HST, pKa = 11.89
A.
pure water
B.
HBO
C.
HST
D.
HMO
E.
HA
Question #10
A 25.0 mL solution of quinine was titrated with 1.00 M Sulfuric acid, H2SO4. It was found that the solution contained 110 mmoles of quinine (a week base). What would be the pOH at equivalence point. Quinine is monobasic with pKb = 5.10.
A.
5.1
B.
9.51
C.
8.9
D.
9.62
E.
None of the choices are correct
F.
4.38
Question #11
A 15.0 mL sample of 0.723 M HClO4 is titrated with a 0.135M Ba(OH)2 solution. The H3O+ concentration after the addition of 75.00mL of Ba(OH)2 is ________ M.
A.
2.2 x 10–2 M
B.
9.6x10-14
C.
2.9 × 10-13
D.
4.6 × 10-13
E.
1.0 × 10-7
Question #12
What volume (in mL) of 0.15M NaOH to you have to add to 50.7 mL of 0.15 M acetic acid (CH3CO2H) to prepare a buffer solution with a pH of 5.02? The pKa of acetic acid is 4.74.
A.
28.74
B.
39.17
C.
25.28
D.
40.25
E.
33.25
Question #13
An unknown student takes 25.0 mL sample of an unknown weak base solution with a an unknown concentration and titrates it with H2SO4 solution. At half-equivalence point the pH is 11.20. It takes 16mL of H2SO4 to reach an equivalence point. What would be the concentration of the unknown weak base sample ________ M if the pOH at equivalence point is 8.12.
A.
1.211
B.
0.452
C.
0.935
D.
0.654
E.
1.069
Question #14
To simulate the pH of blood, which is 7.29, an undergraduate researcher in a biology lab produced a buffer solution by dissolving sodium dihydrogen phosphate and disodium hydrogen phosphate together in an aqueous solution. What mole ratio of Na2HPO4/NaH2PO4 did she need to use? Ka2 = 6.2 x 10–8 and Ka3=3.6 x 10–13
A.
0.9
B.
1.6
C.
None of the choices are correct
D.
0.96
E.
1
F.
1.2
Question #15
Which of the following titrations result in a acidic solution at the equivalence point?
A.
NaOH titrated with HNO3, HClO3 titrated with NaOH
B.
HI titrated with NaCH3CO2 , Ba(NO2)2 titrated with HCl
C.
HBr titrated with Ba(OH)2, NaOH titrated with HNO3
D.
None of the above
Question #16
If the pKa of HCHO2 is 3.74 and the pH of an HCHO2/NaCHO2 solution is 3.54, which of the following is TRUE?
A.
[HCHO2] < [NaCHO2]
B.
[HCHO2] = [NaCHO2]
C.
Does not have enough information to tell
D.
[HCHO2] > [NaCHO2]
E.
It is not possible to make a buffer of this pH from HCHO2 and NaCHO2.
Question #17
A solution containing CaCl2 is mixed with a solution of Li2C2O4 to form a solution that is 2.1 × 10-5 M in calcium ion and 4.75 × 10-5 M in oxalate ion. What will happen once these solutions are mixed forming the concentrations given above? Ksp (CaC2O4) = 2.3 × 10-9.
A.
A precipitate will form since Qsp > Ksp for calcium oxalate.
B.
Nothing will happen since both calcium chloride and lithium oxalate are soluble compounds.
C.
There is not enough information to determine.
D.
Nothing will happen since calcium oxalate is extremely soluble.
E.
No precipitant will form since Qsp < Ksp
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