Chemistry Problem Set: D37
Salts in Solution – Buffers & Review for May 1st Test
Block: ____ Name: ________________
Read section 19.5 pages 618-622. Quest Hwk 10 is due on April 29th at 6 pm.
Our next test is on Wednesday May 1st. The test will cover everything that we have covered on acids and bases (which also
includes Le Chatelier’s Principle and Keq). On May 1st, you need to turn in the following Problem Sets (PS): D31, D32, D33,
D34, D35, and D37. Please staple them in sequential order with D31 on top. You should already have turned in PS D36 as
part of your Titration Lab.
1.
2.
3.
4.
5.
6.
7.
8.
Molarity (section 16.2)
a. Solve problems involving the molarity of a solution. Including the calculation of molarity and use of the dilution
equation. Understand how molarity fits into acid/base problems.
Equilibrium and Keq (section 18.2)
a. Understand how how concentration changes of reactants and products impacts Keq.
b. Solve Keq problems and be able to explain what the magnitude of Keq means.
Le Chatelier’s Principle (section 18.2)
a. Be able to predict the shift of the equilibrium position of a reaction if temperature, concentration, or pressure
changes.
Acid-Base Theories (section 19.1)
a. Know the simple properties of acids and bases.
b. Be able to compare and contrast the definitions of acids and bases using the Arrhenius and Bronsted-Lowry
theories.
c. Know roles played by the hydrogen ion, hydronium ion, and hydroxide ion. Be able to use the terms conjugate
acid/conjugate base.
Hydrogen Ions and Acidity (section 19.2)
a. Know Kw and its dependence on [H+] and [OH-]. Understand that Kw is a Keq and hence our previous work with
Keq’s applies to Kw.
b. Be able to classify a solution as acid, basic, or neutral based on hydrogen ion and hydroxide ion concentration.
c. Be able to compute pH and pOH values (pH + pOH = 14).
Strengths of Acids and Bases (section 19.3)
a. Be able to define (in words and with Ka) and identify strong and weak acids.
b. Be able to define (in words and with Kb) and identify strong and weak bases.
c. Be able to use Ka or Kb to order the strengths of acids or bases.
Neutralization Reactions (section 19.4)
a. Be able to define the products of an acid/base reaction.
b. Be able to explain how an acid/base titration can be used to determine the concentration of an acid or base.
c. Be able to explain the concept of a neutralization reaction.
d. Be able to use the terms end point and equivalence point in a titration.
e. Be able to perform titration (neutralization) computations.
Salts in Solutions & Buffers (section 19.5)
a. Be able to identify if a solution of a salt is acidic or basic.
b. Describe how buffers resist pH changes using reactions and Le Chatlelier’s principle.
1.
What is the Arrhenius definition of an acid and a base? Why is it not used so much today?
2.
What is the Bronsted-Lowry definition of an acid and a base? Why is used so much today?
3.
Using the Bronsted-Lowry theory, write separate reactions for the reaction of nitric acid with water and ammonia with
water.
4.
Determine the pH of the following solutions:
5.
6.
a.
[H+] = 0.0025 M
b.
[H+] = 3.65 x 10-5 M
c.
0.045 M HNO3
d.
0.0056 M H2SO4
e.
[OH-] = 0.0025 M
f.
2.5 M NaOH
Determine the [H+] for each solution:
a.
pH = 3.6
b.
pOH = 11.4
Determine the [OH-] for each solution:
a.
pH = 4.1
b.
pH = 12.1
7.
What is meant by a strong acid ? Weak acid? Strong base? Weak base?
8.
What happens when equal moles of a strong acid and strong base react? Write a reaction.
9.
Suppose you neutralized 100 mL of 0.5 M sulfuric acid with 0.1 M sodium hydroxide. How many mLs would you use?
10. A 15 mL solution of NaOH was completely neutralized by 23.5 mL of 0.1 M HCl. What is the concentration of the base?
11. Suppose you mixed the following together in enough water to create 200 L of solution: 25 g Ca(OH) 2 ; 31.5 g NaNO3 ; and
10.1 g HCl What is the final pH?
12. In a neutralization reaction of a strong acid or base with another strong base or acid …
a.
the salts made from the conjugate bases of strong acids are __________ (acidic, neutral, basic). E.g. _________
b.
the salts made from the conjugate acids of strong bases are __________(acidic, neutral, basic). E.g. __________
13. Fill in the table below (the answers to #12 should help you out here):
Salt
Formula
Corresponding Weak
Acid or Weak Base
Salt solution is Acidic,
Basic, or Neutral
Sodium Acetate
NaCl
NaHCO3
Ammonium Nitrate
(NH4)2SO4
Sodium Sulfate
NH4Cl
14. At the equivalence point (think very carefully here) ….
a. A strong acid titrated with a strong base yields a solution that is __________ (acidic, neutral, basic).
b.
A weak acid titrated with a strong base yields a solution that is __________ (acidic, neutral, basic).
c.
A weak base titrated with a strong acid yields a solution that is __________ (acidic, neutral, basic).
15. How is a buffer prepared? What is so incredibly special and important about buffers?
16. Write the balanced aqueous neutralization reactions for the following and determine whether the solution is acidic,
neutral or basic at the end point:
a. Nitric acid and potassium hydroxide
b.
Acetic acid and sodium hydroxide
c.
Ammonia and sulfuric acid
d.
Calcium hydroxide and hydrochloric acid
Numerical Answers in order …. (check on-line for others):
2.6 4.4 1.35 1.95 11.4 14.4 2.5E-4 2.5E-3 1.26E-10 1.26E-2 250 0.1567 11.33