Download UNIT 7 – CHEMICAL REACTIONS

UNIT 7 – CHEMICAL REACTIONS
REACTIONS AND EQUATIONS (pp. 192 - 200)
1. A ________________________ is simply a chemical change. It is the process by which one or more
substances are changed into one or more different substances.
2. The original substances are known as ____________________ while the resulting substances are called
____________________.
3. Evidence of a chemical reaction can come in the form of things you can see, smell and hear. But, this
does not mean a reaction has actually taken place. To verify a reaction has occurred one must analyze the
products to verify their physical and chemical properties.
4. Chemical reactions release or absorb energy:
5. Atoms are rearranged in a chemical reaction:
6. Particles must collide for a chemical reaction to occur.
WRITING CHEMICAL EQUATIONS (pp. 200 - 207)
1. Reactions can be described with word equations, but it is more convenient to use chemical symbols and
formulas for elements and compounds.
2. A correctly written ___________________________ describes exactly which and how many atoms are
rearranged during the course of a reaction.
3. Atoms and mass are conserved in chemical reactions.
4. Coefficients written in front of the reactants and products indicate the amounts of each that are present.
5. When trying to write a correct equation, _______________ change the products or reactants either by
adding new ones or by changing the subscripts and identities of the formulas in the equation.
6. A _______________ is a numeral used in a chemical equation to indicate relative amounts of reactants
and products.
7. The process of inserting coefficients to satisfy the law of conservation of mass is referred to as
______________________________.
8. Balancing a formula equation turns it into a chemical equation.
Symbols Used in Chemical Equations
1. Chemists make use of symbols to write chemical equations. These are:
Writing a Balanced Equation
1. Write the word equation, showing all of the reactants and products:
2. Write the correct symbols and formulas for all the reactants and products:
3. Count the number of atoms of each element for both sides of the equation:
4. Insert coefficients for atoms of one element at a time so that the law of conservation of mass is satisfied:
5. Repeat step 4 until the law of conservation of mass holds for all of the elements in the equation.
6. Make sure there are equal numbers of atoms of each element on both sides of the equation.
***** Write balanced equations for the following reactions:
a. Chromium (III) sulfate combines with potassium phosphate to form potassium sulfate and chromium
(III) phosphate.
b. Calcium hydroxide and hydrochloric acid react to produce calcium chloride and water.
c. Aluminum sulfate and calcium hydroxide react to produce aluminum hydroxide and calcium sulfate.
***** Balance the following equations:
a. ______NaClO3 (s) → ______ NaCl (s) + ______ O2 (g)
b. _____ Pb(NO3)2 (aq) + _____ NaCl (aq) → _____ PbCl2 (s) + _____ NaNO3 (aq)
c. _____ C3H8 (l) + _____ O2 (g) → _____ CO2 (g) + _____ H2O (l)
d. _____ Al (s) + _____ Fe2O3 (s) → _____ Al2O3 (s) + _____ Fe (s)
Other Information From Equations
1. In addition to information regarding the physical states of the products and reactants, balanced equations
can tell the chemist other things.
2. Reaction conditions are indicated by placing information above and below the arrow:
CLASSIFYING CHEMICAL REACTIONS (pp. 235 - 243)
1. Chemists classify chemical reactions in order to organize the many reactions that occur.
2. Knowing the categories of chemical reactions can help one remember and understand them. It can also
help one recognize patterns and predict products.
Synthesis Reactions
1. In this type of reaction, two elements combine to produce a new compound:
2. Two compounds can also combine to form one compound:
3. A compound and an element can combine to form one compound:
Combustion Reaction
1. A reaction between an element or compound and oxygen can be classified as a combustion reaction.
2. In a ____________________ oxygen combines with a substance and releases energy in the form of heat
and light.
3. Oxygen appears as a reactant in the form __________.
4. Examples are:
Decomposition Reactions
1. A _________________________ is one in which a simple compound breaks down into two or more
elements or new compounds:
2. Decomposition reactions often require an energy source such as heat, light or electricity.
3. Examples:
Single-Replacement Reactions
1. A reaction in which the atoms of one element replace the atoms of another element in a compound is
called a ______________________________.
2. It looks like:
3. Another type of single-replacement reaction involves a metal replacing the hydrogens in water:
4. The third type of single-replacement reaction involves a halogen replacing another halogen:
5. Sometimes a metal will not always replace another metal in a compound dissolved in water.
6. This is because metals differ in their reactivities. A metal’s reactivity is its ability to react with another
substance.
7. Chemists use an _________________________ to be able to know which metals will replace others
during a reaction.
8. The more reactive metals are at the top of the list and the less reactive metals are at the bottom. Metals
can replace other metals below them on the list, but not vice versa.
9. The halogens are also represented on this activity series and the same top to bottom rule applies.
Activity Series for Metals and Non-metals
Single Replacement Reactions
Name
Symbol
Metals
Lithium
Sodium
Potassium
Rubidium
Barium
Strontium
Calcium
Li +
Na+
K+
Rb+
Ba+2
Sr+2
Ca+2
Magnesium
Aluminum
Manganese
Zinc
Chromium
Iron
Cadmium
Cobalt
Nickel
Tin
Lead
Mg+2
Al+3
Mn
Zn+2
Cr+3
Fe
Cd+2
Co+2
Ni+2
Sn
Pb
Hydrogen
H2
Antimony
Bismuth
Copper
Mercury
Silver
Platinum
Gold
Sb
Bi
Cu
Hg
Ag+1
Pt
Au
Non-metals
Fluorine
Chlorine
Bromine
Iodine
F2
Cl2
Br2
I2
Decreasing activity
↓
reacts with water and
acids
reacts with acids
replacing hydrogen
fairly unreactive
Double-Replacement Reactions
1. A reaction in which an exchange of ions between two compounds takes place is called a
______________________________.
2. It looks like:
3. The anions have switched places and are now bonded to the other cations in the reaction. The positive
and negative ions of two compounds switch places.
4. All double-replacement reactions produce a precipitate, a gas or water.
***** Classify each of the following reactions:
Ti (s) + 2Cl2 (g) → TiCl4 (s)
AgNO3 (aq) + LiI (aq) → AgI (s) + LiNO3 (aq)
2C2H2 (g) + 5O2 (g) → 4CO2 (g) + 2H2O (g)
2H2O2 (aq) → 2H2O (l) + O2 (g)
3Mg (s) + 2Cr(NO3)2 (aq) → 3Mg(NO3)2 (aq) + 2Cr (s)
REACTIONS IN AQUEOUS SOLUTIONS (pp. 214 – 223; pp. 226 - 230)
1. Many reactions involve substances dissolve in water. When a substance dissolves in water, a solution
forms. A solution is a homogeneous mixture.
2. A solution contains one or more substances called _______________ dissolved in water. Water is the
_______________, the most plentiful substance in the solution.
Aqueous Solutions
1. Although water is always the solvent in aqueous solutions, there are many possible solutes.
2. Some solutes are molecular compounds that exist as molecules in aqueous solutions.
3. Other solutes are molecular compounds that form ions when they dissolve in water.
Reactions That Form Precipitates
1. Some reactions that occur in aqueous solutions produce precipitates.
2. To show the details of reactions that involve ions in aqueous solutions, chemists use ionic equations.
Ionic equations are ones in which ions in solution are written as ions in the equation.
3. An ionic equation that shows all of the particles in a solution as they realistically exist is called a
_________________________.
4. Notice that some of the ions are both reactants and products and do not participate in the reaction. Ions
that do not participate in a reaction are called ____________________.
5. Ionic equations that include only the particles that participate in the reaction are called
____________________.
***** Write chemical, complete ionic and net ionic equations for the following reactions that produce
precipitates.
a. Aqueous solutions of potassium iodide and silver nitrate are mixed, forming the precipitate silver iodide.
b. Aqueous solutions of aluminum chloride and sodium hydroxide are mixed, forming the precipitate
aluminum hydroxide.
c. Aqueous solutions of lithium sulfate and calcium nitrate are mixed, forming the precipitate calcium
sulfate.
Reactions That Form Water
1. Some reactions in aqueous solution form water which increases the number of solvent particles.
***** Write chemical, complete ionic and net ionic equations for the reactions between the following
substances, which produce water:
a. Sulfuric acid and aqueous potassium hydroxide.
b. Nitric acid and aqueous ammonium hydroxide.
c. Phosphoric acid and aqueous magnesium hydroxide.
Reactions That Form Gases
1. A third type of double-replacement reaction that occurs in aqueous solutions results in the formation of a
gas.
***** Write chemical, complete ionic and net ionic equations for these reactions.
a. Perchloric acid reacts with aqueous potassium carbonate.
b. Sulfuric acid reacts with aqueous sodium cyanide.
c. Nitric acid reacts with aqueous potassium rubidium sulfide.