NAME ___________________________________
GRADED: MINI-PRE-QUIZ: ACID/BASE
DIRECTIONS: Use your notes …. Use your brains …Use the internet …. Use the calculator ….You-s shall be
graded. You are each to work independently for 5 to 8 minutes.
place answers in this
space
____________/ 26
___1) Which of the following accounts for the observation that the pH of pure water is 6.55 at 50.0°C?
1) The autoionization of water is an exothermic process, and shifts to the right as temperature increases
2) At 50.0 °C the [OH] > [H3O+]
3) At 50.0 °C pure water ionizes to a lesser degree
4) The Kw for water at 50.0°C is larger than 1.0 x 10-14
___2) Given: CH3CO2H + H2O ⇄ H3O+ + CH3CO2- Ka = 1.8 x 10-5
Adding 1.0 mL of which of the following would increase the percent ionization of a 50.0 mL sample
of a 1.0 M solution of the weak acid, ethanoic (acetic) acid, in water?
1)
2)
3)
4)
distilled water
1.0 M NaC2H3O2
1.0 M HCl
5.0 M CH3CO2H
___3) Study the following Lewis structures for
nitrous acid (left) and nitric acid (right).
Which of the following statements identifies
the stronger acid and correctly identifies a factor
that contributes to its being the stronger acid?
1) HNO3(aq) is the stronger acid because its molecules experience stronger London Dispersion Forces
2) HNO3(aq) is the stronger acid because the additional electronegative oxygen atom on the nitrogen
stabilizes the conjugate base
3) HNO2(aq) is the stronger acid because its molecules experience weaker London Dispersion Forces
4) HNO2(aq) is the stronger acid because the lone pair of electrons on the nitrogen stabilizes the
conjugate base.
___4) Which of the following is true?
1)
2)
3)
4)
Ka and percent ionization can each be used to determine pH
Percent ionization is dependent upon [HA] and changes as molarity changes
As a solution becomes more dilute the percent ionization increases
ALL OF THESE
Turn this over and keep going…..
___5) To maximize the yield in a certain manufacturing process, a solution of a weak monoprotic acid that has
a concentration between 0.20 M and 0.30 M is required.
Four 100. mL samples of the weak acid at different concentrations are each titrated with 0.20 M NaOH(aq).
The volume of NaOH needed to reach the end point for each sample is given in the table above. Which
solution is the most suitable to maximize the yield?
Acid
Volume of NaOH Added
Solution
(mL)
A
40
B
75
C
115
D
200
1) A
2) B
3) C
4) D
___6) A 0.20-molar solution of a weak monoprotic acid, HA, has a pH of 3.00. The ionization constant of this
acid is…
1) 5.0 x 10−7
2) 2.0 x 10−7
3) 5.0 x 10−6
4) 5.0 x 10−3
5) 2.0 x 10−3
Hint 1: * Write the equation for the
dissociation of the acid and for the
Ka for this weak acid
Hint 2:* The pH is 3 so you can find
the [H3O+], by taking the inverse log
(see your flashcard hints at the end
of Unit 4 (2)
Hint 3:*Based upon the reaction
equation, you should note that
[H3O+] = [A-] … and that
HA = 0.2 -[H3O+] …plug into the Ka
and solve.
___7) HSO4− + H2O ⇄ H3O+ + SO42− In the equilibrium represented above, the species that act as bases
include which of the following?
I. HSO4−
1) II only
II. H2O
2) III only
III. SO42−
3) I and II
4) I and III
5) II and III
___8) What is the H+(aq) concentration in 0.05 M HCN(aq)? (The Ka for HCN is 5.0 x 10−10)
1) 2.5 x 10−11 2) 2.5 x 10−10 3) 5.0 x 10−10 4) 5.0 x 10−6 5) 5.0 x 10−4
____9) Commercial vinegar was titrated with NaOH solution to determine the content of acetic acid, HC2H3O2.
For 20.0 milliliters of the vinegar, 32.0 milliliters of 0.500-molar NaOH solution was required. What
was the concentration of acetic acid in the vinegar if no other acid was present?
1) 1.60 M
2) 0.800 M
3) 0.640 M
4) 0.600 M
5) 0.400 M
10) What are the formulae of the major species in an aqueous solution of 0.10 M C2H4O2? (there are 4)
ans: _____________________________________________
___11) Given:
You will notice that 5 of the hydrogen atoms on this
molecule are labeled with the letters A, B , C, D, or E
Of these choices, which is (are) the most acidic hydrogen?
12) Rank the following from least acidic to most acidic: NH3
ans: ___________________________________
least
most
13) Rank the following from least acidic to most acidic:
ans: ___________________________________
least
most
CH4
H2O HCl