DATE __________________
NOTES-049B-IN CLASS PRACTICE
CHEM 110 (BEAMER)
Last Name
Do Date
First Name
Section
M
T
W
R
Notes-49B: Balancing Equations
In Class Practice
In Class Practice Questions
1)
Write the number of atoms of each substance before and after the reaction is balanced.
(unbalanced)
HCl(g)
+
Al(s)
H atoms
+
Al atoms

Br atoms
AlCl3(s)
+
H2(g)
Al atoms
+
H atoms
Br atoms
Br atoms
(balanced)
6
HBr(g)
+
H atoms
+
2
Al(s)
2

Al atoms
Br atoms
2)
AlBr3(s)
+
Al atoms
+
3
H2(g)
H atoms
Br atoms
Write the number of atoms of each substance before and after the reaction is balanced. Assume oxygen is XS.
(unbalanced)
XS
C3H8O(l)
+
O2(g)
C atoms
+
O atoms
∆
→
H atoms
H2O(g)
+
CO2(g)
H atoms
+
C atoms
O atoms
O atoms
total O
atoms
O atoms
total O
atoms
(balanced)
2
C3H8O(l)
+
C atoms
+
9
XS
O2(g)
O atoms
H atoms
O atoms
∆
→
8
H2O(g)
+
H atoms
+
O atoms
total O
atoms
6
CO2(g)
C atoms
O atoms
total O
atoms
Page 1 of 4
DATE __________________
3)
NOTES-049B-IN CLASS PRACTICE
CHEM 110 (BEAMER)
Write the number of atoms of each substance before and after the reaction is balanced.
(unbalanced)
Ca(OH)2(aq)
+
NbCl5(aq)
Ca atoms
+
OH– ions
CaCl2(s)
+
Nb(OH)5(s)
Nb atoms
Ca atoms
+
Nb atoms
Cl atoms
Cl atoms

OH– ions
Note: If a polyatomic ion appears on both sides, you can balance them as a unit!
(balanced)
5
Ca(OH)2(aq)
+
Ca atoms
+
2
NbCl5(aq)
OH– ions
5
CaCl2(s)
+
Nb atoms
Ca atoms
+
Cl atoms
Cl atoms

2
Nb(OH)5(s)
Nb atoms
OH– ions
Balancing Equations: Hydrocarbon Combustion Reactions
NOTE:
4)
REMEMBER TO PREDICT THE NAMES FIRST. THEN, WRITE THE CHEMICAL FORMULAS FROM THE NAMES.
Predict the product(s) and balance the equation. Remember to check if you can reduce. Do your “Housekeeping.”
XS
4A)
C2H6(g)
+
O2(g)
∆
→
HOUSEKEEPING
VL
4B)
C5H8(g)
+
O2(g)
∆
→
HOUSEKEEPING
LR
4C)
C10H22O2(l)
+
O2(g)
∆
→
HOUSEKEEPING
Page 2 of 4
DATE __________________
NOTES-049B-IN CLASS PRACTICE
CHEM 110 (BEAMER)
Balancing Equations: Decomposition of a Metal Hydrogen Carbonate
NOTE:
5)
5A)
REMEMBER TO PREDICT THE NAMES FIRST. THEN, WRITE THE CHEMICAL FORMULAS FROM THE NAMES.
Predict the product(s) and balance the equation. “Reduce-check” and “Do your Housekeeping.”
Ba(HCO3)2(s)
∆
→
HOUSEKEEPING
5B)
Potassium bicarbonate powder decomposes. Predict the product(s), and write and balance the chemical
equation. “Reduce-check” and “Do your Housekeeping.”
HOUSEKEEPING
5C)
Balance the equation below. “Reduce-check” and “Do your Housekeeping.”
Al2(HCO3)3(s)
∆
→
Al2(CO3)3(s)
+
H2CO3(aq)
HOUSEKEEPING
5D)
Predict the product(s) and balance the equation. “Reduce-check” and “Do your Housekeeping.”
V2(HCO3)5(s)
∆
→
HOUSEKEEPING
Page 3 of 4
DATE __________________
NOTES-049B-IN CLASS PRACTICE
CHEM 110 (BEAMER)
Balancing Equations: General
NOTE:
REMEMBER TO PREDICT THE NAMES FIRST. THEN, WRITE THE CHEMICAL FORMULAS FROM THE NAMES.
Instructions

Balance the following equations. “Reduce-check” and “Do your Housekeeping.”

Scoring:

One incorrect coefficient gives you half credit.

Two or more incorrect coefficients: no credit.

Always do “Housekeeping”

Practice Max Time: Average of 2 min/question

Exam Max Time: Average of 1 min/question
6)
P4O10(s)
7)
Na2SO4(s)
8)
Li(s)
+
H2O(l)
+
+
H3PO4(aq)

Ni(C2H3O2)3(aq)
P4(s)
Ni2(SO4)3(s)

+
NaC2H3O2(aq)
Li3P(s)

9)
NH4ClO4(s)

N2(g)
+
Cl2(g)
10)
Ca(OH)2(s)
+
H3AsO4(aq)

N2H3(CH3)2(l)

+
Ca3(AsO4)2(s)
O2(g)
+
+
H2O(g)
H2O(l)
The “Muscle Through”:
11)
N2O4(l)
+
H2O(g)
+
N2(g)
+
CO2(g)
Page 4 of 4