CHM 1025C Module Five Pretest 1 Name: ___________________

CHM 1020 Path 4 Chapter 9 Study Pack Part 1

Chapter 9: Chemical Equations

A1.Classifying Chemical Reactions- Answers

B. Balancing Chemical Equations Answers

B1.Predicting Single Replacement Products Answers

B2.Predict Double Replacement Answers

B3 Neutralization/Gas Forming Reactions Answers

Conceptual Chemistry Chapter 9 Video Links
Chapter 9: How Chemicals React
9.1 Chemical Reactions Are Represented
      by Chemical Equations
9.2 Counting Atoms and Molecules By Mass
9.3 Converting Between Grams and Moles
9.4 Chemical Reactions Can Be Exothermic
      or Endothermic
9.5 Chemical Reactions Are Driven By Entropy
9.6 Chemical Reactions Can Be Slow or Fast
9.7 Catalysts Speed Up the Destruction
       of Stratospheric Ozone

Evidence for Chemical Reactions

There are four observations that indicate a chemical reaction is taking place:

1. A gas is produced.

Gas may be observed in many ways in a reaction from light fizzing to heavy bubbling.

2. An insoluble solid is produced in a solution.

a. A substance dissolves in water to give an aqueous solution.

b. If we add two aqueous solutions together, we may observe the production of a solid substance.

c. The insoluble solid formed is called a precipitate

3. A permanent color change is observed.

a. Many chemical reactions involve a permanent color change.

b. A change in color indicates that a new substance has been formed

4. An energy change is observed

a. A reaction that releases heat is an exothermic reaction.

b. A reaction that absorbs heat is an endothermic reaction.

c. Examples of a heat energy change in a chemical reaction are heat and light being given off.

Path 4 Chapter 9 Study Packet

In Chapter Four we studied the composition of an atom. In Chapter 3 & 5 we made compounds. Now for Chapter 9 we finally should be able to react these compounds in chemical reactions (or chemical change). The basic symbiology of a chemical reaction is explained in Section 9.1

What are reactants? What are products. What does the arrow between mean? How do we indicate the phase of the chemical? Look at Table 8.1 below summarizes the symbols of a chemical reaction.

Path 4 Chapter 9 Study Packet

Chapter 9 Part A Basic Stoichiometry Definitions

Fill in the following with the symbols used in chemical equations which has the stated translation or meaning(s):

_________1. Produces, yields, gives

_________2. Reacts with, added to, plus

_________ and _________ 3. Solid substance or precipitate forms

_________and _________4. Gaseous substance formed

_________5. Liquid Substance

________5a. Water or aqueous solution

_________6. Reversible Reaction

_________7. No Reaction

8. Show the symbol for heat:__________

9. How would you show a catalyst in a chemical reaction where A plus B forms products D and E, but is catalyzed by substance C

A + B à D + E

10. Define Catalyst (See Section 7.2 page 191)

Path 4 Chapter 9 Study Packet

To start let’s look at 4 five types of reactions: Combination, Decomposition, Single Replacement, Double Replacement, and Neutralization reactions are introduced..

There is a third type of double replacement (Metathesis or Ion Exchange):

Gas Forming Reactions.

When predicting the products of a double replacement reaction, sometimes one of the products instantly decomposes.

If H₂CO₃ is a predicted product in ion exchange, it is written as

CO₂ and H₂O.

For example:

Na₂CO₃ (aq) + HCl (aq) à [H₂CO₃](aq) + NaCl (aq)

Should be written:

Na₂CO₃ (aq) + HCl (aq) à CO₂(g) + H₂O (l) + NaCl (aq)

Two other products which are shown differently:

[NH₄OH] à NH₃ + H₂O

[H₂SO₃] à SO₂ + H₂O

Path 4 Chapter 9 Study Packet

In chapter 12, there is a seventh type of chemical reaction:

Combustion – a substance burns in the presence of oxygen. Combustion of a compound that contains C and H (or C, H, and O) produces carbon dioxide gas and water.

CH₂O(l) + O₂(g) → CO₂(g) + H₂O(l)

The general type of combustion problem looks like this:

C_xH_y [(l) or (g)] + O₂ (g) à CO₂(g) + H₂O (g)

C_xH_yO_z[(s) or (l) or (g)] + O₂ (g) à CO₂(g) + H₂O (g)

The chemical reaction for the combustion of gasoline:

C₈H₁₈ (l) + O₂ (g) à CO₂(g) + H₂O (g)

Octane oxygen gas carbon dioxide water

Path 4 Chapter 9 Study Packet

Chapter 9 Part A1: Classification of Chemical Reactions

Classify Each of the following (unbalanced) chemical reactions as:

Combination (or synthesis)
Decomposition (or Anaylsis)
Single Replacement
Double Replacement (Precipitation)
Double Replacement (Neutralization)
Double Replacement (Gas Forming)
Combustion of a hydrocarbon

______1. Fe + FeCl₃ à FeCl₂

____2_.HCl + Mg(OH)₂ à MgCl₂ + HOH

_____3. Mg + HNO₃ à Mg(NO₃)₂ + H₂

_____4. H₂ + N₂ à NH₃

____5. NaHCO₃ + HCl à NaCl + CO₂ + H₂O

____6. Ca(NO₃)₂ + K₃PO₄ à Ca₃(PO₄)₂ + KNO₃

____7. KClO₃ à KCl + O₂

____8. Na + H₂O à NaOH + H₂

9. Write a chemical equation for solid cadmium hydrogen carbonate decomposing to yield solid cadmium carbonate, water, and carbon dioxide gas:

10. Write a chemical equation for the reaction of aqueous solutions of potassium chromate and calcium sulfate to give the precipitate calcium chromate and aqueous potassium sulfate.

Path 4 Chapter 9 Study Packet

Writing Chemical Reactions

11. Write a chemical equation or solid sodium hydrogen carbonate decomposing to yield solid cadmium carbonate, water, and carbon dioxide gas:

12. Write a chemical equation for the reaction of aqueous solutions of potassium chromate and lead(II) nitrate to give the precipitate lead(II) chromate and aqueous potassium nitrate.

Rules and Suggestions for Balancing Equations

1) The same # and type of atom must be present on each side of the equation.

2) Balancing is accomplished by adding coefficients. NEVER change the subscripts.

3) Coefficients must be in the smallest whole # ratio.

4) Balancing is done by trial and error.

5) Usually Balance H’s and O’s last or an element that appears in more than one place of either side of the reaction .

6) Balance polyatomic ions as one unit in Ion Exchange reactions.

Path 4 Chapter 9 Study Packet

Example of balancing an Equation:

Chapter 9-Part B Balancing Chemical Equations

Balance the following chemical equations (write the chemical formulas in #10 then balance):

1. Fe + FeCl₃ à FeCl₂

2. Al + O₂ à Al₂O₃

3. Na₂CO₃ + C + N₂ à NaCN + CO

4. FeS + O₂ à Fe₂O₃ + SO₂

5. IBr + NH₃ à NI₃ + NH₄Br

6. Cl₂ + HOH à HCl + HClO

7. AgNO₃ à AgNO₂ + O₂

8. HClO₄ + P₄O₁₀ à H₃PO₄ + Cl₂O₇

9. HCl + Mg(OH)₂ à MgCl₂ + HOH

10. Sodium hydroxide + Hydrochloric acid à sodium chloride + water

You may check your work using the online chemical equation balancer at:

http://people.emich.edu/bramsay1/ccc-release/chem.html

Video:
https://www.khanacademy.org/test-prep/mcat/physical-processes/stoichiometry/v/balancing-chemical-equations

M-5i Study Packet

Path 4 Chapter 9 Study Packet

If you were to (H₂O) in the activity series like an acid is shown as (H), where would you put it? Show below:

Given the following Activity Series:

Li > K > Ba > Sr > Ca > Na > Mg > Al >

Mn > Zn > Fe > Cd > Co > Ni > Sn >

Pb > (H) > Cu > Ag > Hg > Au

The rule to follow is a single replacement reaction takes place only if the metal or (H) is more active than the metal or (H) it is replacing. Li will react with everything, while Hg will replace only gold. And poor gold does not react with any of the cations of metals. Therefore gold is found pure in nature, while the very active metals such as potassium and sodium are never found pure in nature, but are found as minerals (ionic compounds).

Will Mg metal react with Nitric Acid? Yes
(Mg has a great reactivity then [H] in the series)

Mg (s) + 2 HNO₃ (aq) → Mg(NO₃)₂ (aq) + H₂ (g)

Will Copper react with Nitric Acid? no
(Cu is below [H] in the activity series)

Cu (s) + HNO₃ (aq) → no reaction

Given the following Active Metals:

Li > K > Ba > Sr > Ca > Na> (H₂O)

The six very active metals are so reactive they will replace one of the two hydrogens in water and form alkaline hydroxides as products. Hydrogen gas will bubble out of the solution. See some of the above movies for demonstrations.

Will Sodium react with water? yes
(Na is one of the six active metals above)

2 Na(s) + 2 HOH (l) → 2 NaOH (aq) + H₂ (g)

Path 4 Chapter 9 Study Packet

Part B1 Single Replacement Reactions

Given the following Activity Series:

Li > K > Ba > Sr > Ca > Na > Mg > Al > Mn > Zn > Fe > Cd > Co > Ni >

Sn > Pb > (H) > Cu > Ag > Hg > Au

Given the following Active Metals:

Li > K > Ba > Sr > Ca > Na

Complete the products of the following reactions, then balance the equation (If no reaction write NR):

1. Cu (s) + Al(NO₃)₃ (aq) à

2. Al (s) + Cu(NO₃)₂ (aq) à

3. Au (s) + H₂SO₄ (aq) à

4. Ca (s) + H₂O (l) à

5. Mn (s) + H₂O (l) à

Path 4 Chapter 9 Study Packet

Part B2 Double Replacement Reactions

Given the following Solubility Rules for Ionic Compounds:

Compounds containing the following ions are generally soluble in water:

1. Alkali metal ions and ammonium ions, Li⁺ , Na⁺ , K⁺ , NH₄⁺

2. Acetate ion, C₂H₃O₂^-

3. Nitrate ion, NO₃^-

4. Halide ions (X), Cl^- , Br^- , I^- (AgX, Hg₂X₂ , and PbX₂ are insoluble exceptions)

5. Sulfate ion, SO₄^2- (SrSO₄, BaSO₄ , and PbSO₄ are insoluble exceptions)

Compounds containing the following ions are generally insoluble in water:

6. Carbonate ion,CO₃^2- (see rule 1 exceptions which are soluble)

7. Chromate ion CrO₄^2- (see rule 1 exceptions which are soluble)

8. Phosphate ion PO₄^3- (see rule 1 exceptions which are soluble)

9. Sulfide ion, S^2- (CaS, SrS, BaS, and rule 1 exceptions are soluble in water)

10. Hydroxide ion, OH^- [ Ca(OH)₂ , Sr(OH)₂ , Ba(OH)₂ , and rule 1 exceptions are soluble)

Complete and balance the following reactions using the above solubility table (write no reaction or NR if both products are soluble or a covalent compounds is not formed)

1. AlCl₃ (aq) + K₂CO₃ (aq) à

2. NiSO₄ (aq) + Li₃PO₄ (aq) à

3. NaCl (aq) + AgNO₃ (aq) à

4. H₂SO₄ (aq) + NaOH (aq) à

5. H₃PO₄ (aq) + Ba(OH)₂ (aq) à

Video:
http://www.brightstorm.com/science/chemistry/chemical-reactions/double-replacement-reactions/

http://www.youtube.com/watch?v=7hVKb4ROjZw

http://www.youtube.com/watch?v=_oixjNeKtxs

http://www.youtube.com/watch?v=IMfNi_C2DTg

http://www.youtube.com/watch?v=2tIutF6-wn4

Path 4 Chapter 9 Study Packet

Part B3 Double Replacement Reaction: