Chapter 17 Test Flashcards
Consider the following reaction between nitrous acid and ammonia:
HNO2(aq) + NH3(aq) NH4No2(aq)
Ka = 4.5 x 10^-4
Kb = 1.8 x 10^-5
What is the equilibrium constant for this reaction?
8.1 × 10^5
Hydrochloric acid can interact with sodium hydroxide to form water and sodium chloride.
HCl(aq) + NaOH(aq) H2O(l) + NaCl(aq)
This reaction involves a strong acid, a strong base, water, and spectator ions not involved in the reaction. Which of the following correctly lists the acid, base, and spectator ions?
acid: HCl;
base: NaOH;
spectator ions: Na+, Cl −
For the reaction
H3O+(aq) + NH3(aq) NH4^+(aq) + H2O(l)
One intermediate reaction is
NH3(aq) + H2O(l) NH4^+(aq) + OH-(aq)
What is the other intermediate reaction that provides the components that add up to the overall reaction?
H3O+(aq) + OH-(aq) 2H2O(l)
The three intermediate reactions (and their K values) and the final (or overall) reaction of acetic acid and ammonia are shown below:
Reaction 2: CH3COOH(aq) + H2O(l) CH3OO-(aq) + H3O+(aq)
(Ka= 1.8 x 10^-5)
Reaction 3: NH3(aq) + H2O(l) NH4^+(aq) + OH-(aq)
(Kb = 1.8 x 10^-5)
Reaction 4: H3O+(aq) + OH-(aq) 2H2O(l)
(Ka = 1/Kw = 1/(1 x 10^-14))
Final Reaction: CH3COOH(aq) [ acetic acid] + NH3(aq) [ammonia] NH4^+(aq) [ammonium ion] + CH3OO-(aq) [acetate ion]
What is the expression and value for KFinal?
KFinal = Ka Kb (1 / Kw ); KFinal = 3.2 × 10^4
Look at the equilibrium curve for the reaction of HA(aq) H+(aq) + A-(aq).
Ka = 1 × 10−10 for this reaction. Which statement about this plot is not true?
[H + ] [A− ] / [HA] at Point 2 < [H + ] [A− ] / [HA] at Point 5 because [A− ] is larger.
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].
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 an acidic buffer (pH < 7) that is formed by adding 1.50 moles of formic acid (HCOOH, Ka = 1.77 × 10−4 ) and 0.50 moles of sodium formate (Na(HCOO)) to water to make 1 L of solution.
HCOOH(aq) + H3O(aq) + HCOO-(aq)
The weak acid in this reaction is formic acid, HCOOH. Its conjugate base, derived by removing an H + ion, is HCOO−. What is the pH of the acidic buffer solution?
3.27
What is the pH of a buffer solution comprised of 2.05 M HCOOH and 1.20 M HCOO− in a 1.0 L solution after 0.10 mol NaOH is added? Ka = 1.77 × 10−4
3.58
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
Look at the graphical representation of a buffer solution.
In this experiment, 0.10 moles of HCl were added to 0.30 moles of NH3 to make 1.0 L of solution. Which of the following correctly lists the buffer capacity of this system?
Range A for strong bases and Range C for strong acids
Look at the graphical representation of our buffer solution.
In this experiment, 0.10 moles of HCl were added to 0.30 moles of NH3 to make 1.0 L of solution. Which of the following best describes the buffer capacity of the system that is generated by this process?
The system’s capacity for buffering strong bases is defined by Range A. The system’s capacity for buffering strong acids is defined by Range C. Within the buffer ranges, the solution has a fairly constant pH value.
Which of the following acid-base pairs would be best for preparing a buffer solution with a pH of 8.15?
pair #4
Suppose that you wanted to prepare a acetate ion / acetic acid buffer solution with a pH of 4.35. What is the value of [A− ] / [HA] for the correct buffer solution for this event? The Ka for acetic acid is 1.8 × 10−5.
0.407
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
