Honors Chemistry
Chapter 3:
Balancing Chemical
Equations
Name: ____________________________________
Mods: ___________________
Chemical Equation Notes:
Parts of a Chemical Equation:
I.
Reactants:
- Appear on the LEFT side of the equation
- Are the original/starting substances in a chemical reaction
II.
Products:
- Appear on the RIGHT side of the equation
- Are the final substances created/produced in a chemical reaction
*** In an equation, the reactants and products are separated by a yield arrow (). If
there are multiple reactants or products, they are separated by a plus sign
III.
The four physical states (at room temperature) of reactants & products are written in
parentheses to the right of each compound in a chemical reaction.
(s)
____________________
(l)
____________________
(g)
____________________
(aq) ____________________ – formed by dissolving/mixing a substance with water
– Acids are always (aq) in reactions
IV.
Law of Conservation of Mass
- Matter/mass cannot be created or destroyed
- Mass of products = Mass of reactants
- Chemical equations must have equal numbers and kinds of atoms on both side
of the arrow … this is why we BALANCE EQUATIONS
V.
Coefficients:
- Used to balance equations
- Indicate how many of each type of compound/substance are involved in a reaction
- When counting total # of atoms, coefficients and subscripts multiply together
- Ex: 2 Al2(CO3)3 means... _____ Al atoms, _____ C atoms, & _____ O atoms
Rules for Balancing Chemical Equations:
1) Determine the correct formulas for all of the reactants and products in the reaction, using
what you know about elements and ionic compounds. The state of matter in which each
reactant and product exists is indicated in parentheses after the chemical formula.
2) Write the formulas for the reactants on the left and the formulas for the products on the
right with a yields sign () in between. If two or more reactants or products are involved,
separate their formulas with plus signs. When finished, you will have a skeleton equation.
3) Count the number of atoms of each element in the reactants and products. For
simplicity, a polyatomic ion appearing unchanged on both sides of the equation is
counted as a single unit.
4) Balance the elements one at a time by placing coefficients in front of each reactant and
product. When no coefficient is written, it is assumed to be 1. It is best to begin the
balancing operation with elements that appear only once on each side of the equation.
You may NEVER attempt to balance an equation by changing subscripts in the
chemical formula of a substance.
5) Check each atom or polyatomic ion to be sure that the equation is balanced.
6) Finally, make sure all the coefficients are in the lowest possible ratio that balances.
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Directions: Balance the following chemical equations:
1.
____ N2 (g) +____ O2 (g)  ____ N2O (g)
2.
____ KI (aq) + ____ Cl2 (g)  ____ KCl (aq) + ____ I2 (s)
3.
____ Mg(NO3)2 (aq) + ____ K3PO4 (aq)  ____ Mg3(PO4)2 (s) + ____ KNO3 (aq)
4.
____MnO2 (s)+ ____HCl (aq)  ____MnCl2 (aq) + ____H2O (l) + ____Cl2 (g)
5.
____Zn(OH)2 (s) + ____H3PO4 (aq)  ____Zn3(PO4)2 (s) + ____H2O (l)
6.
____ C2H6 (g) + ____ O2 (g)  ____ CO2 (g) + ____ H2O (g)
7.
____ C3H8 (g) + ____ O2 (g)  ____ CO2 (g) + ____ H2O (g)
8.
____ C6H12O6 (s) + ____ O2 (g)  ____ CO2 (g) + ____ H2O (g)
Balancing Equations Practice
1)
____ Na3PO4 (aq) + ____ KOH (aq)  ____ NaOH (aq) + ____ K3PO4 (aq)
2)
____ MgF2 (aq)+ ____ Li2CO3 (aq) ____ MgCO3 (s) + ____ LiF (aq)
3)
____ P4 (s) + ____ O2 (g)  ____ P2O3 (s)
4)
____ RbNO3 (aq) + ____ BeF2 (aq)  ____ Be(NO3)2 (aq) + ____ RbF (aq)
5)
____ AgNO3 (aq) + ____ Cu (s)  ____ Cu(NO3)2 (aq) + ____ Ag (s)
6)
____ CF4 (s)+ ____ Br2 (g) ____ CBr4 (s) + ____ F2 (g)
7)
____ HCN (aq) + ____ CuSO4 (aq)  ____ H2SO4 (aq) + ____ Cu(CN)2 (aq)
8)
____ GaF3 (aq) + ____ Cs (s) ____ CsF (aq) + ____ Ga (s)
9)
____ BaS (aq) + ____ PtF2 (aq)  ____ BaF2 (aq) + ____ PtS (s)
10)
____ N2 (g) + ____ H2 (g)  ____ NH3 (g)
11)
____ NaF (aq) + ____ Br2 (g)  ____ NaBr (aq) + ____ F2 (g)
12)
____ Pb(OH)2 (aq) + ____ HCl (aq)  ____ H2O (l) + ____ PbCl2 (s)
13)
____ AlBr3 (aq) + ____ K2SO4 (aq)  ____ KBr (aq) + ____ Al2(SO4)3 (aq)
14)
____ CH4 (g) + ____ O2 (g)  ____ CO2 (g) + ____ H2O (g)
15)
____ Na3PO4 (aq) + ____ CaCl2 (aq)  ____ NaCl (aq) + ____ Ca3(PO4)2 (aq)
16)
____ K (s) + ____ Cl2 (g)  ____ KCl (aq)
17)
____ Al (s) + ____ HCl (aq)  ____ H2 (g) + ____ AlCl3 (aq)
18)
____ N2 (g) + ____ F2 (g)  ____ NF3 (g)
19)
____ SO2 (g) + ____ Li2Se (s)  ____ SSe2 (g) + ____ Li2O (s)
20)
____ NH3 (g) + ____ H2SO4 (aq)  ____ (NH4)2SO4 (aq)
21)
____ KClO3 (aq)  ____ KCl (aq) + ____ O2 (g)
22)
____ NaCl (aq) + ____ F2 (g)  ____ NaF (aq) + ____ Cl2 (g)
23)
____ H2 (g) + ____ O2 (g)  ____ H2O (g)
24)
____ C4H10 (l) + ____ O2 (g)  ____ CO2 (g) + ____ H2O (g)
25)
____ C8H18 (l) + ____ O2 (g)  ____ CO2 (g) + ____ H2O (g)
26)
____ FeCl3 (aq) + ____ NaOH (aq)  ____ Fe(OH)3 (s) + ____ NaCl (aq)
27)
____ P (s)+ ____O2 (g)  ____ P2O5 (s)
28)
____ Na (s) + ____ H2O (l)  ____ NaOH (aq) + ____ H2 (g)
29)
____ Ag2O (s)  ____ Ag (s) + ____ O2 (g)
30)
____ S8 (s) + ____O2 (g)  ____ SO3 (g)
31)
____ C3H8O (s) + ____O2 (g)  ____ CO2 (g) + ____ H2O (g)
32)
____ K (s) + ____ MgBr2 (aq)  ____ KBr (aq) + ____ Mg (s)
33)
____ HCl (aq) + ____ CaCO3 (s)  ____ CaCl2 (aq) + ____H2O (g) + ____ CO2 (g)
34)
____ HNO3 (aq) + ____ NaHCO3 (s)  ____ NaNO3 (aq) + ____ H2O (g) + ____ CO2 (g)
35)
____ H2O (l) + ____ O2 (g)  ____ H2O2 (l)
36)
____ NaBr (aq) + ____ CaF2 (aq)  ____ NaF (aq) + ____ CaBr2 (aq)
37)
____ H2SO4 (aq) + ____ NaNO2 (aq)  ____ HNO2 (aq) + ____ Na2SO4 (aq)
38)
____ Al (s) + ____ Fe3N2 (aq)  ____ AlN (aq) + ____ Fe (s)
39)
____ C7H8 (s) + ____ O2 (g)  ____ CO2 (g) + ____ H2O (g)
40)
____ NaClO3 (aq)  ____ NaCl (aq) + ____ O2 (g)
Chemical Reactions – Word Equations
You must remember the following SEVEN diatomic molecules when writing equations!!!!!
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Directions: Write the word equations below as chemical equations and balance:
1)
When lithium hydroxide pellets are added to a solution of sulfuric acid, aqueous lithium
sulfate and water are formed.
2)
If a copper coil is placed into a solution of silver nitrate resulting in the formation of silver
crystals and a solution of copper (I) nitrate.
3)
A combustion reaction occurs between liquid pentanediol, C5H17O2, and oxygen gas.
4)
Aqueous aluminum bromide and chlorine gas react to form aqueous aluminum chloride
and bromine gas.
5)
Zinc metal and aqueous lead (II) nitrate react to form aqueous zinc nitrate and lead.
7)
Aqueous solutions of sodium phosphate and calcium chloride react to form solid calcium
phosphate and aqueous sodium chloride.
8)
Potassium metal and chlorine gas combine to form solid potassium chloride.
9)
Aluminum metal and hydrochloric acid react to form aqueous aluminum chloride and
hydrogen gas.
10)
Aqueous calcium hydroxide and phosphoric acid react to form solid calcium phosphate
and water.
11)
Copper and sulfuric acid react to form aqueous copper (II) sulfate, water vapor, and
gaseous sulfur dioxide.
12)
Hydrogen gas and gaseous nitrogen monoxide react to form water vapor and nitrogen
gas.
13)
Solid potassium chlorate when heated yields solid potassium chloride and oxygen gas.
14)
Hydrogen gas plus oxygen gas yields water.
15)
Nitrogen gas plus hydrogen gas yields gaseous ammonia.
16)
Nitrogen gas plus oxygen gas react to form gaseous dinitrogen pentoxide.
17)
Iron plus aqueous lead (II) sulfate react to form aqueous iron (II) sulfate plus lead.
18)
Sulfuric acid decomposes to form sulfur trioxide gas plus water.
19)
Solid sodium oxide combines with water to make aqueous sodium hydroxide.
20)
Aqueous potassium iodide reacts with bromine forming aqueous potassium bromide plus
iodine.
21)
Aqueous sodium phosphate reacts with aqueous calcium nitrate to produce aqueous
sodium nitrate plus solid calcium phosphate.
22)
Zinc reacts with aqueous iron (III) chloride yielding aqueous zinc chloride plus iron.
23)
Aqueous ammonium carbonate and aqueous magnesium sulfate react to yield aqueous
ammonium sulfate plus solid magnesium carbonate.
24)
Aluminum plus oxygen gas form solid aluminum oxide.