Free Study Guide for
Cracolice • Peters
Introductory Chemistry: An Active Learning Approach
Second Edition
www.brookscole.com/chemistry
Chapter 17
Net Ionic Equations
Chapter 17–Assignment A: Solution Conductivity and Inventories, Strong Acids
and Weak Acids
Some solutes exist in water as molecules, and some solutes exist in water as ions. You need
to know which solutes exist in which form to describe reactions that occur in water. Here
are some ideas that lead you to this awareness:
1)
A solute may be classified as a strong electrolyte, a weak electrolyte, or a
nonelectrolyte according to the ability of its water solution to conduct electricity.
2)
If a solution conducts electricity, ions must be present as solute particles.
3)
When a strong acid dissolves, it dissociates into ions. The major species present
in the solution are ions, and the minor species present is un-ionized molecules.
4)
There are seven common strong acids. Their names and formulas must be
memorized.
5)
If an acid is not one of the seven strong acids, it is a weak acid.
6)
When a weak acid dissolves, it does not dissociate into ions to a large extent. The
solution inventory is mainly un-ionized molecules.
Learning Procedures
Study
Sections 17.1–17.3. Focus on Goals 1–4 as you study.
Strategy
This material is mostly conceptual. Study the figures and the captions in
Section 17.1 carefully. The summary box at the end of Section 17.3 is
particularly important.
Answer
Questions, Exercises, and Problems 1–6. Check your answers with those
at the end of the chapter.
Workbook
If your instructor recommends the Active Learning Workbook, do
Questions, Exercises, and Problems 1–6.
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Chapter 17
Net Ionic Equations
Chapter 17–Assignment B: Net Ionic Equations
Both silver nitrate and sodium chloride are colorless, clear solutions. When silver nitrate and
sodium chloride solutions are mixed, a white solid forms. The solid is pure silver chloride,
and remaining in solution are sodium ions and nitrate ions. In this assignment, you will
learn to write an equation that describes this process, identifying only the reactants and
products, showing only the chemical change that has occurred.
An equation that shows precisely what happens in a solution reaction, and no more, is called
a net ionic equation. To write net ionic equations you must first be able to write conventional
equations, which you learned to do in Chapter 8. From that starting point, you must know
about the new ideas in this assignment:
1)
Strong acids and ionic compounds designated (aq) in a conventional equation are
rewritten in a total or net ionic equation with the formulas of the major species in
solution.
2)
A total ionic equation is made into a net ionic equation by removing the spectators,
those species that are on both sides of the total ionic equation.
3)
Prediction of a single-replacement redox reaction is made by referring to an activity
series.
4)
Prediction of an ion combination that yields a precipitate can be made from a
solubility table or from solubility rules.
5)
Prediction of an ion combination that yields a molecular product is made from the
difference between strong and weak acids. Weak acids, including water, are formed
from strong acids, but strong acids cannot be formed from weak acids.
6)
When ion combinations yield unstable substances, the right side of the net ionic
equation has the formulas of the stable decomposition products.
Learning Procedures
Study
Sections 17.4–17.11. Focus on Goals 5–9 as you study.
Strategy
Work through the text and examples, then focus on Table 17.5, which
summarizes the entire chapter. Practice by writing many net ionic equations.
Answer
Questions, Exercises, and Problems 7–36. Check your answers with those at
the end of the chapter.
Workbook
If your instructor recommends the Active Learning Workbook, do
Questions, Exercises, and Problems 7–36.
Chapter 17–Assignment C: Summary and Review
The ability to write correct net ionic equations is probably the most important predictor of
success in general chemistry, especially the second term. Consequently, the advice in this
chapter is long, to make certain you understand this topic.
127
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Study Guide for Introductory Chemistry: An Active Learning Approach
Start with Table 17.5, Summary of Net Ionic Equations. You should be able to recognize
reaction types, given reactants.
To write major species in solution, you must be able to predict which species consist of ions
and which consist of neutral molecules. The table below summarizes the relationships
among electrolytes, solution inventories, electrical conductivity, and solutes.
Electrolyte
Major Species
Conductivity
Solute Types
Strong
Ions
Good
All soluble ionic compounds
The seven strong acids
Weak
Neutral molecules
Poor
Weak acids
Nonelectrolyte
Neutral molecules
Nonconductor
Un-ionized compounds
Net ionic equations is another of those topics where, if you develop a systematic approach,
you will have little difficulty. Here are some very strong suggestions about writing net ionic
equations:
1)
Follow closely the three-step Procedure: Writing a Net Ionic Equation in Section
17.4 in the text. Students who don't attempt to shortcut the procedure in the learning
process are far more successful than those who do. Put another way, all students
who have trouble have one thing in common: they shortcut the procedure.
2)
For each species in the conventional equation (Step 1), write the state designation,
(g), (l), (s), or (aq). This is very important.
3)
In writing the total ionic equation (Step 2), repeat all species designated in the
conventional equation as (g), (l), or (s) in exactly the same form. Do not change
them.
4)
Be sure you know the difference between strong and weak acids, and be sure you
can decide if a given acid is strong or weak. Memorize the seven strong acids.
5)
If a species designated (aq) in the conventional equation is an ionic compound or a
strong acid, rewrite that species with separate ions in the total ionic equation. If a
species designated (aq) in the conventional equation is a weak acid, repeat it in the
total ionic equation in exactly the same form, not separated into ions.
6)
When you eliminate spectators from the total ionic equation to make the net ionic
equation (Step 3), do just that. Eliminate only those things that appear on both sides
of the equation; don't change anything else.
7)
Be sure the net ionic equation is balanced in both atoms and electrical charge.
8)
Reduce the net ionic equation to lowest terms by dividing all coefficients by a
common factor, if any.
128
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Chapter 17
Net Ionic Equations
Learning Procedures
Review
your lecture and textbook notes.
the Chapter in Review and the Key Terms and Concepts, and read the Study
Hints and Pitfalls to Avoid.
Answer
Concept-Linking Exercises 1–3. Check your answers with those at the end
of the chapter.
Electrolyte-Classification Exercises 1–12. Check your answers with those at
the end of the chapter.
Questions, Exercises, and Problems 37–38. Check your answers with those
at the end of the chapter.
Workbook
There are no additional summary and review problems in the workbook for
Chapter 17.
Take
the chapter summary test that follows. Check your answers with those at the
end of this assignment.
Chapter 17 Sample Test
Instructions: You may use a “clean” periodic table. You may use a solubility table if your
instructor allows it.
1)
A soluble salt is a _____ electrolyte.
a) weak
b) nonc) strong
2)
Write the formulas of the ions present in solutions of the following compounds:
a) calcium chloride
b) hydroiodic acid
c) acetic acid, HC2 H3 O2
d) aluminum nitrate
Questions 3–8: Write the net ionic equation for each reaction that occurs, if any. Write
NR if no reaction occurs.
3)
Solutions of sodium sulfate and potassium carbonate are mixed.
129
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Study Guide for Introductory Chemistry: An Active Learning Approach
4)
Hydrochloric acid is added to ammonium carbonate solution.
5)
Sodium formate solution, NaCHO2 (aq), is added to hydrobromic acid.
6)
Lead(II) nitrate and nickel sulfate solutions are mixed.
7)
Solid calcium hydroxide is treated with nitric acid.
8)
Hydroiodic acid is poured on nickel metal (hydrogen gas is below nickel metal in
the activity series).
130
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Chapter 17
Net Ionic Equations
Answers to Chapter 17 Sample Test
1)
c
2)
a)
b)
c)
d)
3)
2 Na+(aq) + SO4 2 –(aq) + 2 K+(aq) + CO3 2 –(aq) Æ NR
4)
2 HCl(aq) + (NH4 )2 CO3 (aq) Æ 2 NH4 Cl(aq) + “H2 CO3 ”
2 HCl(aq) + (NH4 )2 CO3 (aq) Æ 2 NH4 Cl(aq) + H2 O(l) + CO2 (g)
2 H+(aq) + 2 Cl– (aq) + 2 NH4 +(aq) + CO3 2 –(aq) Æ
2 NH4 +(aq) + 2 Cl– (aq) + H2 O(l) + CO2 (g)
2 H+(aq) + CO3 2 –(aq) Æ H2 O(l) + CO2 (g)
5)
NaCHO2 (aq) + HBr(aq) Æ NaBr(aq) + HCHO2 (aq)
Na+(aq) + CHO2 – (aq) + H+(aq) + Br– (aq) Æ Na+(aq) + Br– (aq) + HCHO2 (aq)
CHO2 – (aq) + H+(aq) Æ HCHO2 (aq)
6)
Pb(NO3 )2 (aq) + NiSO4 (aq) Æ PbSO4 (s) + Ni(NO3 )2 (aq)
Pb2+(aq) + 2 NO3 – (aq) + Ni2+(aq) + SO4 2 –(aq) Æ
PbSO4 (s) + Ni2+(aq) + 2 NO3 – (aq)
2+
2–
Pb (aq) + SO4 (aq) Æ PbSO4 (s)
7)
Ca(OH)2 (s) + 2 HNO3 (aq) Æ Ca(NO3 )2 (aq) + 2 HOH(l)
Ca(OH)2 (s) + 2 H+(aq) + 2 NO3 – (aq) Æ Ca2+(aq) + 2 NO3 – (aq) + 2 H2 O(l)
Ca(OH)2 (s) + 2 H+(aq) Æ Ca2+(aq) + 2 H2 O(l)
8)
2 HI(aq) + Ni(s) Æ NiI2 (aq) + H2 (g)
2 H+(aq) + 2 I– (aq) + Ni(s) Æ Ni2+(aq) + 2 I– (aq) + H2 (g)
2 H+(aq) + Ni(s) Æ Ni2+(aq) + H2 (g)
CaCl2 : Ca2+(aq) + 2 Cl– (aq)
HI: H+(aq) + I– (aq)
HC2 H3 O2 : HC2 H3 O2 (aq)
Al(NO3 )3 : Al3+(aq) + 3 NO3 – (aq)
131
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