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Example Questions
Example Question #51 : Acid Base Reactions
Put the following acids in order of their DECREASING acid strength: HOCl, HO2Cl, HO3Cl, HO4Cl.
HOCl, HO4Cl, HO2Cl, HO3Cl
HOCL, HO2Cl, HO3Cl, HO4Cl
HO4Cl, HO3Cl, HO2Cl, HOCl
HO2Cl, HOCl, HO3Cl, HO4Cl
HO4Cl, HOCl, HO2Cl, HO3Cl
HOCL, HO2Cl, HO3Cl, HO4Cl
For an oxyacid, the acid strength increases as the number of oxygens increase.
Example Question #91 : Reaction Types
Put the following in order of INCREASING acid strength: H2Se, KH, AsH3, HBr.
HBr, H2Se, AsH3, KH
KH, H2Se, AsH3, HBr
AsH3, H2Se, HBr, KH
KH, AsH3, H2Se, HBr
AsH3, H2Se, KH, HBr
KH, AsH3, H2Se, HBr
Acid strength increases going across a period.
Example Question #61 : Acid Base Reactions
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?
A-
HA
H3O+
Equal amounts of acid and conjugate base are present.
H2A+
HA
Since pH < pKa the undissociated acid is the predominant form.
Example Question #2 : Ph And Pka
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.
A-
H3O+
HA
H2A+
A-
Since pH > pKA, the deprotonated form of the acid is predominant.
Example Question #3 : Ph And Pka
Carbonic acid as a pKa1 = 6.35 and a pKa2=10.33. If the pH is 3.52, what is the predominant species present.
HCO3-
Can not be determined.
H2CO3
CO32-
H3O+
H2CO3
Since pH < pKa1, the undissociated form of carbonic acid (H2CO3) is predominant.
Example Question #4 : Ph And Pka
Sulphurous acid (H2SO3) has a pKa1 = 1.92 and a pKa2 = 7.18, if the pH = 5.3, what is the predominant species present?
Can not be determined
H2SO3
SO32-
H3O+
HSO3-
HSO3-
Since pH > pKa1 but pH < pKa2 the predominant form is one with a single hydrogen dissociated.
Example Question #5 : Ph And Pka
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?
Can not be determined
H3PO4
PO43-
H2PO4-
HPO42-
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?
Increase the pH in the cathode.
Adding SnCl2 to the cathode.
All of the above.
Lowering the pH in the cathode.
Increasing the H2 pressure in the cathode.
All of the above.
All of these changes would change Q and thus change the measured cell potential.
Example Question #71 : Thermodynamics
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.
Smaller
Identical
Can not be determined
Larger
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.
Can not be determined
Identical
Larger
Smaller
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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