## Quiz: Acids and bases.

Cracolice 2/e Ch 18.

Quiz is "closed book" except for PT & calculator.
Kw = 10-14 M2.
Show clear work for all calculations. Use proper SF.
Write balanced equations; show phases.

1. a. Write the equation for the proton transfer reaction that would occur between nitric acid and the fluoride ion.

b. In your equation, label each chemical species as an acid or a base. Then mark the conjugate acid-base pairs.

c. Which of the two acids in this equation is stronger? How do you know?

2. a. Write the equation for the proton transfer reaction that would occur between H2 and H2+, with the H2+ serving as the acid. You can omit phases for now. [Caution: Don't be confused by the unusual chemicals here. Follow the information that is given in the question. If you find the chemical formulas tricky, you might think of H2+ as H-H+.]

b. In your equation, label each chemical species as an acid or a base. Then mark the conjugate acid-base pairs.

3. Calculate the pH of a solution that has [OH-] = 5.71x10-3 M. (Keep 2 decimal places in your calculated pH.)

4. You have an aqueous solution of nitric acid, HNO3, a strong acid. Which one of the following "lists" best represents the species that are in the solution? (They all have the same amount of HNO3, just in different forms. Which form is most correct?) Briefly explain how you can tell.

Explanation of "artwork". In the following lists, HNO3 represents unionized nitric acid molecules, and H+    NO3- represents ionized nitric acid. Of course, with ionized nitric acid, the two ions are not really together anymore; showing them "near" each other is an artistic simplification to help you see how many of each species is present.

i. H+    NO3-       H+    NO3-       H+    NO3-       H+    NO3-       H+    NO3-       H+    NO3-       H+    NO3-       H+    NO3-

ii. HNO3       HNO3       H+    NO3-       HNO3       HNO3       H+    NO3-       HNO3       HNO3

iii. HNO3       HNO3       HNO3       HNO3       HNO3       HNO3       HNO3       HNO3

iv. none of the above. Explain (that is, you provide the proper list, and explain why).

5. Each part below describes two solutions. In each part, tell which is more acidic. Briefly explain and/or show work as appropriate in each case. (That is, if you need to calculate something, show the work. If not, explain your answer. Answers without explanations are unacceptable.)

Assume that the temperature is about 25° C.

a. pH = 10.4 and pH = 10.1

b. pH = 3 and [H+] = 10-2 M

c. pH = 3.8 and [H+] = 2.4x10-4 M

d. [H+] = 10-2 M and [OH-] = 10-13 M

e. pH = 10 and [OH-] = 10-9 M

f. 0.1 M hydrochloric acid and 0.1 M propanoic acid (If one of those is unfamiliar, it shouldn't matter. You should be able to answer this anyway.)

g. pH = 1 and pH = -1

6. This question is a follow-up to the previous one. It uses the information given there.

a. In the previous question, which of all the solutions listed in the various parts are acidic? That is, list all of the acidic solutions from the previous question (all parts).

b. The statement of the previous question said to assume that the temperature was 25° C. How did you make use of that information in answering the question? Give a specific example. [This may be an "advanced" question for some who are just starting chemistry.]

7. You have a solution of sodium hydroxide, of unknown concentration. You titrate 25.00 mL of it with 0.2513 M hydrochloric acid; the titration takes 12.24 mL to reach equivalence.

a. Write the equation for the titration reaction.

b. Qualitatively, which is more concentrated, the acid solution or the base solution? Explain how you can tell from the data -- without doing any calculations at this point.

c. How many moles of hydrochloric acid did you use in the titration?

d. Calculate the concentration of the sodium hydroxide solution. Check that your result agrees with your prediction in part b.

Last update: August 28, 2019