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Example Questions
Example Question #91 : Reaction Types
Put the following acids in order of their DECREASING acid strength: HOCl, HO2Cl, HO3Cl, HO4Cl.
HO4Cl, HOCl, HO2Cl, HO3Cl
HO4Cl, HO3Cl, HO2Cl, HOCl
HOCL, HO2Cl, HO3Cl, HO4Cl
HOCl, HO4Cl, HO2Cl, HO3Cl
HO2Cl, HOCl, HO3Cl, HO4Cl
HOCL, HO2Cl, HO3Cl, HO4Cl
For an oxyacid, the acid strength increases as the number of oxygens increase.
Example Question #92 : Reaction Types
Put the following in order of INCREASING acid strength: H2Se, KH, AsH3, HBr.
KH, AsH3, H2Se, HBr
KH, H2Se, AsH3, HBr
HBr, H2Se, AsH3, KH
AsH3, H2Se, HBr, KH
AsH3, H2Se, KH, HBr
KH, AsH3, H2Se, HBr
Acid strength increases going across a period.
Example Question #91 : Reaction Types
If you have a solution that consist of a weak monoprotic acid (HA), with a pKA of 5.3 and a pH of 3.2, what is the predominant species present?
H3O+
Equal amounts of acid and conjugate base are present.
H2A+
HA
A-
HA
Since pH < pKa the undissociated acid is the predominant form.
Example Question #92 : Reaction Types
If you have a solution that consists of a monoprotic acid (HA), with a pKa of 4.1 and at a pH of 5.8, what is the predominant species present?
Equal amounts of acid and conjugate base are present.
H3O+
H2A+
HA
A-
A-
Since pH > pKA, the deprotonated form of the acid is predominant.
Example Question #93 : Reaction Types
Carbonic acid as a pKa1 = 6.35 and a pKa2=10.33. If the pH is 3.52, what is the predominant species present.
CO32-
Can not be determined.
HCO3-
H3O+
H2CO3
H2CO3
Since pH < pKa1, the undissociated form of carbonic acid (H2CO3) is predominant.
Example Question #94 : Reaction Types
Sulphurous acid (H2SO3) has a pKa1 = 1.92 and a pKa2 = 7.18, if the pH = 5.3, what is the predominant species present?
HSO3-
H2SO3
Can not be determined
H3O+
SO32-
HSO3-
Since pH > pKa1 but pH < pKa2 the predominant form is one with a single hydrogen dissociated.
Example Question #95 : Reaction Types
Phosphoric acid has a pKa1 = 2.15, a pKa2 = 7.20, and a pKa3 = 12.35. If the pH = 13.0, what is the predominant species present?
HPO42-
Can not be determined
H3PO4
H2PO4-
PO43-
PO43-
Since pH > pKa1, pKa2, and pKa3 the predominant form of the acid is the fully deprotonated form.
Example Question #1 : Cell Potential Under Non Standard Conditions
Consider an electrochemical cell that has the following overall reaction:
2 H+(aq) + Sn (s) -> Sn2+ (aq) + H2 (aq)
Which of the following changes would alter the measured cell potential?
Adding SnCl2 to the cathode.
Increasing the H2 pressure in the cathode.
Lowering the pH in the cathode.
All of the above.
Increase the pH in the cathode.
All of the above.
All of these changes would change Q and thus change the measured cell potential.
Example Question #672 : Ap Chemistry
For the following cell reaction:
2 Al (s) + 3 Mn2+ (aq) -> 2 Al3+ (aq) + 3 Mn (s)
predict if the cell potential Ecell will be larger, or smaller than Eocell for the following conditions:
[Al3+] = 2.0 M; [Mn2+] = 1.0 M.
Can not be determined
Smaller
Larger
Identical
Smaller
Altering these conditions would increase Q, and thus result in a decrease in the measured cell potential.
Example Question #2 : Cell Potential Under Non Standard Conditions
For the following cell reaction:
2 Al (s) + 3 Mn2+ (aq) -> 2 Al3+ (aq) + 3 Mn (s)
predict if the cell potential Ecell will be larger, or smaller than Eocell for the following conditions: [Al3+] = 1.0 M; [Mn2+] = 5.0 M.
Smaller
Can not be determined
Identical
Larger
Larger
At these concentrations Q will become smaller, and thus log Q will become smaller. This will give rise to a larger cell potential.
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