All AP Chemistry Resources
Example Questions
Example Question #91 : Reaction Types
Put the following acids in order of their DECREASING acid strength: HOCl, HO2Cl, HO3Cl, HO4Cl.
HOCL, HO2Cl, HO3Cl, HO4Cl
HO4Cl, HO3Cl, HO2Cl, HOCl
HO2Cl, HOCl, HO3Cl, HO4Cl
HO4Cl, HOCl, HO2Cl, HO3Cl
HOCl, HO4Cl, HO2Cl, HO3Cl
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.
HBr, H2Se, AsH3, KH
AsH3, H2Se, KH, HBr
KH, AsH3, H2Se, HBr
AsH3, H2Se, HBr, KH
KH, H2Se, AsH3, HBr
KH, AsH3, H2Se, HBr
Acid strength increases going across a period.
Example Question #93 : 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+
A-
HA
Equal amounts of acid and conjugate base are present.
H2A+
HA
Since pH < pKa the undissociated acid is the predominant form.
Example Question #94 : 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.
H2A+
HA
H3O+
A-
A-
Since pH > pKA, the deprotonated form of the acid is predominant.
Example Question #95 : 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.
H2CO3
HCO3-
Can not be determined.
H3O+
CO32-
H2CO3
Since pH < pKa1, the undissociated form of carbonic acid (H2CO3) is predominant.
Example Question #96 : 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?
SO32-
Can not be determined
H2SO3
HSO3-
H3O+
HSO3-
Since pH > pKa1 but pH < pKa2 the predominant form is one with a single hydrogen dissociated.
Example Question #1 : 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?
HPO42-
H2PO4-
H3PO4
Can not be determined
PO43-
PO43-
Since pH > pKa1, pKa2, and pKa3 the predominant form of the acid is the fully deprotonated form.
Example Question #61 : Acid Base Reactions
Which of the following is a Lewis base?
BF3
Me3B
NH3
B2H6
NH3
NH3 should be the clear correct choice, since it is the only one having a pair of electrons that are available. The rest of the answer choices are all Lewis acids.
Example Question #62 : Acid Base Reactions
What is the defining characteristic of Bronsted-Lowry bases?
Proton (H+) donor
Dissociates in solution to give the OH– ion
Proton (H+) acceptor
Electron pair acceptor
Dissociates in solution to give the H+ ion
Proton (H+) acceptor
The definition of a Bronsted-Lowry base is a species that has the ability to gain, or accept a proton (H+). Dissociating in solution is part of the Arrhenius definition of acids and bases, and Lewis acid are electron pair acceptors.
Example Question #63 : Acid Base Reactions
Which of the following can act as a Lewis base?
NH2NH2
BF3
HF
CH3COOH
NH2NH2
A Lewis base is an electron-pair donor. N atoms have a valence of 5, and in the NH2NH2 compound, it is only bonded to another N atom and 2 H, so it's only using 3 of its 5 valence electrons to form these bonds. Thus, each nitrogen has a pair of unbonded electrons and can act as a Lewis base.