Download Balancing Equations Practice

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SCI404 Enriched Review
Nomenclature
Write the formula for the following compounds:
a) Iron (II) oxide
b) Calcium Iodide
c) Nitrogen trioxide
d) Magnesium nitrate
e) Calcium carbonate
Name the following compounds:
a) ZnSO4
b) MgF2
c) CuCl2
d) N2F3
e) NaO
Balancing Equations Practice
Write the formulas for the compounds and balance the equations.
1) sulphur tetrafluoride + water  sulphur dioxide + hydrogen fluoride
2) magnesium + hydrochloric acid  magnesium chloride + hydrogen gas
3) copper(II)carbonate + hydrochloric acid  carbon dioxide + water +
copper(II)chloride
4) copper(II)sulphate + iron  copper + iron(II)sulphate
5) sodium hydroxide + sulphuric acid  sodium sulphate + water
6) zinc + sulphuric acid  zinc sulphate + hydrogen gas
7) Sodium chloride + silver nitrate  sodium nitrate + silver chloride
Name_____________
Conversion to Mol
It is important to understand how to convert to mol so that you can do
stoichiometry properly. First, use the periodic table to calculate the molar mass (in
g/mol). Then divide the mass that you are given by the molar mass.
Avogradro’s number (1 mol) = 6.02 X 1023
1)
a)
b)
c)
d)
e)
What is the mass of:
1 mol of sodium atoms?
10 mol of carbon atoms?
0.1 mol of silver atoms?
0.5 mol of iron atoms?
0.125 mol of magnesium atoms?
2) How many mol of atoms are there in
f) 27 g of aluminum?
g) 20 g of calcium?
h) 4 g of potassium?
i) 140 g of copper?
j) 0.65 g of zinc?
3) What is the molecular mass of:
k) oxygen (O2) ?
l) carbon dioxide?
m) hydrogen iodide?
n) silicon tetrachloride?
4)
o)
p)
q)
r)
What is the mass of:
1.7 mol of chlorine (Cl2) ?
0.022 mol of water?
0.5 mol of sulphur molecules (S8) ?
0.25 mol of phosphorus molecules (P4) ?
5) How many mol are there in:
s) 6.4 g of sulphur dioxide?
t) 56 g of carbon monoxide?
6)
u)
v)
w)
How many particles are there in:
2.5 mol of lithium atoms
42 g of calcium atoms
23 g of water
Name_____________
Answers:
a) 23 g b) 120 g c) 10.8 g d) 28 g e) 3.04 g f) 1 mol g) 0.5 mol h) 0.1 mol i) 2.2 mol j) 0.01
mol k) 32 g/mol l) 44 g/mol m) 128 g/mol n) 169.8 g/mol o) 120.7 g p) 0.396 g q) 128 g r) 31 g
s) 0.1 mol t) 2 mol u) 1.5 x 1024 v) 6.3 x 1023 w) 7.69 X 1023
Stoichiometry Practice
These problems involve three main steps:
1) Convert whatever is given to mol.
2) Use ratios from the equation to predict how many mol of the unknown are
produced or needed.
3) Convert these new mol to whatever units are desired [usually mass (g)]
Balance the equation, and complete the stoichiometry question.
1) If 20 grams of zinc reacts with excess hydrochloric acid, how many grams of zinc chloride are
produced? (41.7g)
Zn + HCl  H2 + ZnCl2
2) How many grams of chlorine gas must be reacted with excess sodium iodide if 10 grams of
sodium chloride are needed? (6.1 g)
Cl2 + NaI  NaCl + I2
3) How many grams of oxygen are produced in the decomposition of 20.4 grams of potassium
chlorate? (8.0 g)
KClO3  KCl + O2
4) How many grams of copper are required to replace 4 grams of silver nitrate? (0.75 g)
Cu + AgNO3  Cu(NO3)2 + Ag
5) If excess ammonium sulfate reacts with 20 grams of calcium hydroxide, how many grams of
ammonia are produced? (9.2 g)
(NH4)2SO4 + Ca(OH)2  CaSO4 + NH3 + H2O
6) If excess sulphuric acid reacts with 30 grams of sodium chloride, how many grams of
hydrogen chloride are produced? (18.7 g)
H2SO4 + NaCl  HCl + Na2SO4
7) How much silver phosphate is produced if 10 grams of silver acetate are reacted with excess
sodium phosphate? (8.36 g)
AgC2H3O2 + Na3PO4  Ag3PO4
+ NaC2H3O2
8) How many grams of sodium hydroxide are needed to completely neutralize 25 grams of
sulphuric acid? (20.4 g)
H2SO4 + NaOH  H2O + Na2SO4
9) How many grams of calcium metal will react completely with 10 grams of water to yield
calcium hydroxide and hydrogen gas? (11.1 g)
Ca + H2O  Ca(OH)2 + H2
10) Zinc chloride is produced by the reaction of HCl with zinc. If 40 grams
of HCl reacts
with an excess of zinc, how much zinc chloride will be produced? (74.7 g)
Zn + HCl  ZnCl2 + H2
11) How many grams of silver chloride will be produced when 85 grams of silver nitrate are
reacted with sodium chloride? (71.7 g)
AgNO3 + NaCl  AgCl + NaNO3
Name_____________
12) If 98.7 grams of KCl are produced, how many grams of chlorine are
needed? (46.4 g)
KBr + Cl2 KCl + Br2
Endothermic and Exothermic Reactions
There are two types of questions here. To find reaction energy (a), add up the
energy in the bonds between the molecules in the products, then in the reactants.
Subtract the total bond energy of the products from the bond energy of the
reactants. If this value (the reaction energy) is negative, it is exothermic, meaning
it releases energy. If the value is positive, it is endothermic, and absorbs energy.
To determine the amount of energy in a particular experiment (b), you need to do a
bit of stoichiometry.
(a) Calculate the reaction energy for the following equations (use the bond energies
table on pg. 115 in your textbook). Also state whether the reaction is endothermic
or exothermic.
1. C2H4 + H2 → C2H6
Chemical formula
Structural Formula
C2H4
C2H6
H2
(-124 kJ, exothermic)
2.
(-2054 kJ, exothermic)
H—H
Name_____________
(b) Determine the amount of energy involved in the following examples:
3. How much energy will be released when 34.0 g of H2O2 decomposes according to
the following equation? (100kJ, exothermic)
2H2O2 2H2O + O2 + 200kJ
4. How much energy will be released when 5.494g of manganese reacts with
hydrochloric acid? (22.1kJ, exothermic)
Mn + 2HCl  MnCl2 + H2 + 221kJ
5. How many kJ of energy will be needed to decompose 10.8 grams of N2O gas?
(13.5kJ, endothermic)
2N2O + 110kJ  4NO2 + O2
Energy
Kinetic Energy: energy of an object in motion.
Ek
1 2
mv
2
Remember: mass (m) must be in kg, velocity (v) must be in m/s. (km/h
 3.6)
1.
Which car has a greater kinetic energy: a 900 kg car travelling at 100 km/h or a
1800 kg car travelling at 50 km/h? (the lighter car)
2. H.C. kicks a soccer ball at 15.0 m/s, giving the ball a kinetic energy of 48.4 J.
What is the ball’s mass? (0.43kg)
Gravitational Potential Energy: energy stored in an object raised above a surface,
based on it’s reference level (usually how far above the Earth it is)
E pg  mgh
(g=9.8N/kg) Mass (m) must be in kg, and height (h) must be in m.
1.
A 2 kg coconut is about to fall off a coconut tree. It is 10 m above the ground.
What is the potential energy of the coconut? (196 J)
2. A 20 gram pencil placed precariously behind a person’s ear has 0.3 J of potential
energy. How high above the ground is the pencil? (1.5 m)
Mechanical Energy: These problems are based upon the Law of Conservation of Energy,
that the energy in a closed system remains constant. Mechanical energy is the sum of
the potential energy and kinetic energy.
E m  E pg  E k and E m1 E m 2 so.. E pg1 E k1 E pg 2  E k 2 .. for this equation, you can cancel
out the mass of the object.
Note: For these problems we are ignoring air resistance and friction.
1.
A physics student (Kevin Gandhi) drops a 200 g snowball out the window of Mr.
Wilder’s classroom, trying to test the laws of gravity and hit Jyoti as she
unknowingly passes under the window. If the window is 30 m above the ground
and the snowball narrowly misses, what is the speed of the snowball just before
it hits the ground. (24 m/s)
Name_____________
Note: If the snowball was accurately dropped, you would need to factor in Jyoti’s
height.
2. A 60 kg diver dives off a diving board at a velocity of 4.00 m/s [down]. What is
the magnitude of his velocity at the moment he hits the water, if the diving
board is 10.0 m above the water? (10.8 m/s)
3. Craig is playing in the WHS intramural basketball final and throws up a 3-pointer
at the buzzer. The ball reaches the basket, which is 3.05 m high with a velocity
of 8 m/s. If the ball left Craig’s hand at a height of 2.20 m, what was it’s initial
velocity? (9 m/s)
Effective Force: The effective force is the component of a force that affects the
motion of the object. A force applied at an angle can be broken down into it’s vertical
and horizontal components.. this is done using the basic trig functions (sin, cos, tan). It
helps to draw a diagram for these problems.
1. A sled is being pulled. The handle makes a 30o angle with the ground. The
force applied on the handle is 50 N. Determine the vertical and horizontal
components of this force. Which component of this force is effective at
helping move the sled forward? (horiz [effective F] = 43.3 N, vert = 25 N)
2. A box with a mass of 5 kg is placed on ramp inclined at 30o above the ground.
What is the effective force that is pulling the box down the ramp. [24.5 N]
Work: W = ΔE, where W is the work, and ΔE is the difference in energy in a system
Also, W = F//d, where: W is the work (in Joules)
F// is the force parallel to the displacement of the object
d is the distance travelled by the object (in meters)
1. A box is pulled 30 m along the ground with a force of 5 N. Calculate the
amount of work done on the box. [150 J]
Kirchoff’s Laws
For Series Circuits: Itotal= I1 =I2 =I3.. Vtotal= V1 +V2 +V3 .. Req= R1 +R2 +R3 ..
For Parallel Circuits: Itotal= I1 + I2 +I3 .. Vtotal= V1 = V2 = V3 .. Req 
1. Given the following electric circuit with four voltmeters.
Voltmeter V1 reads 2.0 V.
Voltmeter V2 reads 4.0 V.
Voltmeter V3 reads 7.0 V.
1
1

..
R1 R2
Name_____________
V1
V2
V4
V3
What is the reading on voltmeter V4? (1.0 V)
2. The following electric circuit consists of two resistors R1 and R2 and a power
source.
R1
R2
Using an ammeter, you measured the current intensity (I) through each resistor.
Here are the results :
Resistor
Intensity (A)
R1
0.75
R2
0.75
Given this information, what is the current intensity provided by the power source
Is? (1.5 A)
3. The following electric circuit consists of a power supply and two resistors (R1 and
R2).
Name_____________
R1
10 Ω
R2
15 Ω
What is the equivalent resistance of this circuit? (6Ω)
4. The following electric circuit consists of a power supply, two resistors (R 1 and R2)
and two ammeters
reads 5 A.
A1
and
AT
. Ammeter
R1
A1
10 
reads 2 A and ammeter
AT
R2
A1 I1 = 2 A
AT
IT = 5 A
What is the equivalent resistance, Req, of this circuit? (4 Ω)
Punnett Squares
When asked to calculate the probabilities of offspring obtaining certain traits, we
use a Punnett Square. For these questions, you need to be very familiar with the
following terms: heterozygous, homozygous, pure-line, dominant, recessive. If the
question does not indicate the letter for the allele, you need to choose one.
1. In rabbits, the allele for long ears (E) is dominant over the allele for short
ears (e). If a short eared rabbit mates with a rabbit that is heterozygous
for the ear length trait, what will be the genotype probabilities of the
offspring? [50% Ee : 50% ee]
2. In bears, the allele for black fur is dominant over the allele for brown fur.
A pure line individual with black fur mates with a bear that is heterozygous
for the fur trait. What will be the genotype probabilities of the offspring?
[50% FF : 50% Ff]
3. In pea plants, yellow seeds (Y) are dominant over green seeds (y), and round
shape (R) is dominant over wrinkled shape (r). Two individuals that are
heterozygous for both traits are crossbred. What are the phenotype
probabilities of the offspring? [ 56% round, yellow seeds : 19% round, green
seeds : 19% wrinkled, yellow seeds : 6% wrinkled, green seeds]