EXAM 2 Flashcards
Consider two solutions, solution A: 1.0 M hydrofluoric acid (HF) and solution B: a mixture of 1.0 M HF and 1.0 M NaF. If a strong base is added to both of these solutions, what will the result be?
Solution A will increase in pH and Solution B’s pH won’t change very much.
Identify the correct statement about an acid–base buffer solution.
All:
A buffer solution resists changes in its pH when an acid or base is added to it.
It can be prepared by combining a weak acid with a salt of its conjugate base.
It can be prepared by combining a weak base with its conjugate acid.
The pH of a buffer solution does not change when the solution is diluted.
Which of these can be mixed together in water to produce a buffer solution?
HClO4 and NaClO4
HNO3 and NaNO3
H2SO4 and NaHSO4
H3PO4 and NaH2PO4
HCl and NaCl
H3PO4 and NaH2PO4
Which of these can be mixed together in water to produce a buffer solution?
NH3 and HCl
HF and KF
HClO3 and NaClO3
HCN and NaOH
ALL!
Which of these would make the best buffer? (Ac = acetate)
a solution of hydrochloric acid and sodium chloride, HCl and NaCl
a solution of acetic acid and ammonia, NaAc and NH3
a solution of acetic acid and ammonium chloride, HAc and NH4Cl
a solution of sodium acetate and ammonium chloride, NaAc and NH4Cl
a solution of ammonia and ammonium chloride, NH3 and NH4Cl
a solution of ammonia and ammonium chloride, NH3 and NH4Cl
Which of the following is a buffer system? Solutions contain roughly equal amounts of each substance
fluoride ion and hydrofluoric acid
bromide ion and hydrobromic acid
phosphide ion and hydrogen phosphate ion
carbonate ion and carbonic acid
phosphoric acid and phosphate ion
fluoride ion and hydrofluoric acid
Which would be the best choice for preparing a buffer with a pH = 8.0?
a solution of formic acid and sodium formate, Ka= 1.8 × 10-4
a solution of acetic acid and sodium acetate, Ka= 1.8 × 10-5
a solution of hypochlorous acid and sodium hypochlorite, Ka= 3.5 × 10-8
a solution of boric acid and sodium borate, Ka= 5.8 × 10-10
All of these solutions would be equally good choices for making this buffer.
a solution of hypochlorous acid and sodium hypochlorite, Ka= 3.5 × 10-8
Which would be the best choice for preparing a buffer with a pH = 3.5?
a solution of formic acid and sodium formate, Ka= 1.8 × 10-4
a solution of acetic acid and sodium acetate, Ka= 1.8 × 10-5
a solution of hypochlorous acid and sodium hypochlorite, Ka= 3.5 × 10-8
a solution of boric acid and sodium borate, Ka= 5.8 × 10-10
All of these solutions would be equally good choices for making this buffer
a solution of formic acid and sodium formate, Ka= 1.8 × 10-4
What is the pH of a buffer solution where [HA] = [A-]?
pH = 1
pH =Ka
pH = pKa
pH = pOH
pH = 7.0
pH = pKa
The pKaof a weak acid was determined by measuring the pH of a solution containing the weak acid at 0.40 M and its conjugate base at 0.60 M. The measured pH was 7.8. What is the pKa of the weak acid?
8.0
7.8
7.6
7.0
7.4
7.6
The pKaof a weak acid was determined to be 3.39 by measuring the pH of a solution containing the weak acid at 0.20 M and its conjugate base. The measured pH was 3.27. What was the concentration of the conjugate base?
0.26 M
0.15 M
0.20 M
0.050 M
0.35 M
0.15M
What is the pHof a solution containing 0.30 M of lactic acid and 0.50 M of lactate ion (Ka for lactic acid = 1.38 ×10-4)?
9.92
10.36
3.86
4.08
3.64
4.08
How many moles of sodium acetate must be added to 500. mL of a 0.25 M acetic acid solution to produce a buffer with a pH of 4.94? The pKa of acetic acid is 4.74. (You can neglect the change in volume when sodium acetate dissolves in the acetic acid solution.)
0.011 moles
0.021 moles
0.125 moles
0.198 moles
0.206 moles
0.198 moles
What are the characteristics of a pH indicator? A pH indicator
is a weak acid.
has different characteristic colors in protonated and unprotonated forms.
changes color when the pH is near its pKa.
none of these answers
all of these
all of these
Acid–base indicators need to have very intense colors so a very low concentration is visible. Could there be a problem in using too much indicator?
No, the colors would just be darker.
No, indicators are inert.
Yes, more indicator requires more extreme pH values to change color.
Yes, the indicator could affect the acid–base chemistry being measured.
No, the colors would just be sharper.
Yes, the indicator could affect the acid–base chemistry being measured.
In a titration of monoprotic acids and bases, there is a large change in pH
at the point where pH = pKa of the acid.
when the volume of acid is exactly equal to the volume of base.
when the concentration of acid is exactly equal to the concentration of base.
when the number of moles of acid is exactly equal to the number of moles of base.
at the point where pH = pKb of the base.
when the number of moles of acid is exactly equal to the number of moles of base.
Halfway to the equivalence point in a titration curve of a weak acid with a strong base,
nothing is happening yet.
the pH = pKa of the weak acid.
pH = 3.5 exactly.
pH = pKa of the indicator.
the pH has not yet changed.
the pH = pKa of the weak acid.
At what point in the following titration curve for a weak acid being titrated with a strong base is the pH equal to the pKa of the acid? The x-axis scale goes from 0.0 mL to 20.0 mL. The sharp rise is at 10.0 mL.
0.0 mL
5.0 mL
9.0 mL
10.0 mL
18.0 mL
5.0mL
A Lewis acid is
a proton donor.
a proton acceptor.
an electron-pair donor.
an electron-pair acceptor.
never viewed also as a Brønsted–Lowry acid.
an electron-pair acceptor
A Lewis base is
an electron-pair acceptor.
an electron-pair donor.
a proton donor.
a proton acceptor.
never viewed also as a Brønsted–Lowry base.
an electron-pair donor
A Lewis base is any species capable of ________ an electron pair.
accepting
donating
creating
neutralizing
gaining
donating
A Lewis acid is any species capable of ________ an electron pair.
accepting
donating
creating
neutralizing
losing
accepting
In this reaction, which species is the Lewis acid?
Cu^2+ + NH3-> Cu(NH3)^2+
Cu2+
NH3
[Cu(NH3)]2+
None of these is an acid.
All of these are acids
Cu2+
Which species is a Lewis base?
H3O+
Na+
BF3
P(CH3)3
NH4+
P(CH3)3
Which species is a Lewis acid?
Cl2
NH3
F-
P(CH3)3
Al3+
Al3+
Which statement about acids and bases is correct?
A Lewis base is an electron-pair donor; a Lewis acid is an electron-pair acceptor.
A Brønsted–Lowry base is a proton acceptor; a Brønsted–Lowry acid is a proton donor.
A Lewis base can accept a proton from a Brønsted–Lowry acid.
Coordinate covalent bonds in transition metal compounds are formed when a Lewis base reacts with a Lewis acid.
All statements are correct.
ALL
Which compound contains a coordinate covalent bond?
Cl2
NH3
H2C=CH2
Co(H2O)6^2+
CH4
Co(H2O)6^2+
Which compound contains a coordinate covalent bond?
PF3
H3NBF3
HCOOH
AlCl3
O2
H3NBF3
The bond between a metal cation and a ligand can best be described as
an ionic bond.
a covalent bond.
a coordinate covalent bond.
a polar covalent bond.
a bidentate bond.
a coordinate covalent bond.
The bonds between the zinc ion and the nitrogen atoms in the complex Zn(NH3)42+ are best described as
ionic.
covalent.
coordinate covalent.
polar covalent.
d-electron bonds.
coordinate covalent.
A ligand is any ________ forming a coordinate bond to a metal cation.
Lewis acid
ion
Lewis base
organic compound
species
Lewis base
Which species is least likely to function as a ligand in a transition metal complex ion?
NH4+
NH3
Cl-
H2O
OH-
NH4+