The three intermediate reactions and the final reaction of acetic acid and ammonia are shown below.
Reaction 2: CH3COOH(aq) + H2O(l) <==> CH3OO-(aq) + H3O+(aq) (Ka = 1.810^-5)
Reaction 3: NH3(aq) + H2O(l) <==> NH4+(aq) + OH-(aq) (Kb = 1.810^-5)
Reaction 4: H3O+(aq) + OH-(aq) <==> 2H2O(l) (Ka = 1/Kw = 1/(1*10^-14))
What is the expression and value for KFinal?
KFinal = Ka Kb (1 / Kw ); KFinal = 3.2 × 10^4
The following reaction represents a buffer system, which responds to the addition of a base or an acid.
CH3COOH(aq) + H2O(l) <==> CH3OO-(aq) + H3O+(aq)
Which statement about this reaction is not correct?
The weak acid acts as a proton (H3O+ ) acceptor; the H3O+ ions come from the addition of the strong acid.
Suppose that you want to prepare an acidic buffer solution. You add 0.93 M Na2HPO4 to 1.23 M KH2PO4. If Ka (for H2PO4− ) = 6.2 × 10^−8, what is the pH of this buffer solution?
7.09
Suppose that you have 1.00 liters of a solution of 1.25 M HCOOH and 0.83 M HCOO−. To the solution you add 0.20 mol HCl. What is the first event that will occur?
HCl will dissociate to its component ions, H + and Cl −. The HCOO− will react with H + (or H3O+ ) ions to form HCOOH
What is the pH difference between a 1.00 L buffer solution (Solution A) of 1.25 M HCOOH and 0.920 M HCOO− and a 1.00 L buffer solution (Solution B) of 2.75 M HCOOH and 0.920 M of HCOO−? when 0.10 moles of HCl is added to both buffer solutions? The Ka = 1.77 × 10−4
0.325
Which characteristic defines the main difference between a basic buffer system and an acidic buffer system?
A basic buffer system is a solution that can maintain a basic pH as more acid or base is added.
Suppose that you have a 75 mL solution of 0.200 M HCl that is being titrated with 0.125 M NaOH. At the point indicated by the arrow, 49 mL of NaOH have been added. What is the pH of the solution at this point?
1.14
Which point on the titration curve for a weak acid shows the point at which we have half of the original amount of weak acid left?
B
Look at Point D in the titration curve for a weak acid.
CH3COOH(aq) + OH-(aq) <==> Ch3COO-(aq) + H2O(l)
Which statement about the reaction at Point D is not true?
The pH at Point D, the equivalence point, is 7.0
Which statement about the deprotonations of a diprotic acid is not correct?
The value of Ka for the first deprotonation event with a diprotic acid is less than the Ka value for the second deprotonation event.
Pb2+ (2.0 × 10−8 moles) is added to a 1 L solution of chromate, CrO42−.
Pb2+(aq) + CrO42-(aq) <==> PbCrO4(s)
(where Ksp = 2.8 × 10−13 )
at which point precipitation begins to occur. What was the concentration of chromate ion in the solution?
1.4 × 10^−5
What is the solubility of aluminum hydroxide,
Al(OH)3, if Ksp for Al(OH)3 is 3.0 × 10−34?
Al(OH)3(s) <==> Al3+(aq) + 3OH-(aq)
1.8 × 10^−9 M
The dissociation reaction for CuBr is
What is the solubility of CuBr in a 0.05 M HBr (strong) acid solution? The Ksp for the dissociation of CuBr(s) is 4.2 × 10−8.
8.4 × 10^−7
Consider the reaction of formic acid and sodium hydroxide.
HCOOH(aq) + NaOH(aq) <==> Na(HCOO)(aq) + H2O(l)
The acid constant, Ka, for formic acid is 1.8*10^-4. From this, calculate the equilibrium constant for the above reaction
1.8 × 10^10
Which statement about the reaction below is not correct?
HA(aq) <==> H+(aq) + A-(aq)
A decrease in [H + ] will cause an increase in [HA].
What is the solubility of CaF in 0.08 M NaF solution? Ksp = 3.9 × 10−11 and the dissociation reaction for CaF2 is
CaF2(s) <==> Ca2+(aq) + 2F-(aq)
6.1 × 10^−9
Which statement about phenolphthalein is not correct?
Phenolphthalein indicator works because there is a protonation event that occurs between the central carbon atom and an oxygen atom.
Adding Ag+ to a 0.10 M chromate CrO42− solution, eventually yields silver chromate, Ag2CrO4(s).
Ag2CrO4(s) <==> 2Ag+(aq) + CrO42-(aq)
(where Ksp = 9.0 × 10−12 )
Which statement about this reaction is not correct?
Initially, when Ag+ is first added, you have a nonprecipitate solution of Ag+ and Ag2CrO4 in equilibrium with each other.
Suppose that you wanted to prepare a buffer solution with a pH of 2.07. Which of the following tells you which acid-base pair to use and how you must alter that acid-base pair to get as close as possible to the pH?
Acid-base pair #1; You would have to increase the [A− ].
Suppose that you wanted to prepare a acetate ion / acetic acid buffer solution with a pH of 5.01. What is the value of [A− ] / [HA] for the correct buffer solution for this event? The Ka is 1.8 × 10^−5
1.86