Download C:\Users\Evan P. Silberstein\Documents\Chemistry\Frisch\Chem R

Chemistry R: Form TR7.13A
Name ______________________________
TEST 7 REVIEW
Date _________________ Period _____
Test Review # 7
Conservation of Mass. Matter is neither created nor destroyed. During a chemical reaction the mass does not change. A properly written
equation shows conservation of mass. For example, AgNO3(aq) + NaCl(aq) ÿ NaNO3(aq) + AgCl(s).
SILVER NITRATE
AgNO3
Ag =
1 × 108 = 108
N =
1 × 14 = 14
O =
3 × 16 = 48
170
SODIUM CHLORIDE
NaCl
Na =
1 × 23 = 23
Cl =
1 × 35 = 35
58
AgNO3(aq)
170
NaCl(aq) ÿ
58
=
228
+
+
SODIUM NITRATE
NaNO3
Na =
1 × 23 = 23
N =
1 × 14 = 14
O =
3 × 16 = 48
85
NaNO3(aq)
85
=
SILVER CHLORIDE
AgCl
Ag =
1 × 108 = 108
Cl =
1 × 35 = 35
143
+
+
AgCl(s)
143
228
Balancing Equations. The equation at the top of the box to the right does not show conservation of mass.
Starting with two molecules of hydrogen, as shown in the equation at the bottom of the box by writing a
coefficient 2 in front of the hydrogen and forming two molecules of water by writing a coefficient 2 in front
of the water shows conservation. Coefficients are used to balance equations. Coefficients make the number
of atoms of each type the same on the reactant and product side. As a result, coefficients make the mass the
same on the reactant and product side of the equation. Balancing is done by counting the number and type of
atoms on the reactant and product side of the equation and making them equal.
Moles. A mole is a formula mass expressed in
Gram Formula
grams. (1 mole = 1 gram formula mass).
Substance
Formula Mass
Atomic mass units are too small to measure on
Mass
a laboratory balance, but grams are not. An
carbon
12 amu
12 g
atom of carbon has a mass of 12 amu and a
58 amu
58 g
molecule of glucose has a mass of 180 amu. sodium chloride
Each mass represents one particle. Since the (NaCl)
mass ratios in formula masses and gram glucose (C H O )
180 amu
180 g
6 12 6
formula masses are the same (12 amu:180
amu::12 g:180 g), the ratio of particles must
still be the same (1mole:1 mole). The gram formula mass (GFM) is the number of grams in 1 mole. This
relationships shown above and to the right.
Stoichiometry. Stoichiometry is the branch of chemistry that
deals with the application of the laws of definite proportions
and of the conservation of mass and energy to chemical
activity. It shows the quantitative relationship between
constituents of a chemical reaction. Stoichiometric
calculations are based on several assumptions. It is assumed
that the reaction has no side reactions, the reaction goes to
completion, and the reactants are completely consumed. One
type of problem that can be solved stoichiometrically is
based on the mole ratios of a balanced equation. A sample
problem is shown to the right.
H 2 + O 2 ÿ H 2O
2 + 32 … 18
2H2 + O2 ÿ 2H2O
2(2) + 32 = 2(18)
36 = 36
g
mole
2. g = GFM × mole
g
3. mole =
GFM
1. GFM =
results in the mathematical
Sample Problem
How many moles of oxygen are consumed when 0.6 moles of
hydrogen burns to produce water?
Step 1: W r i t e
a balanced
equation and determine
the mole ratios from the
equation
Step 2: Identify the known and
the unknown
Step 3: Set up a proportion and
solve for the unknown
2 H2(g)
mole
ratio
moles
2
+ O2(g)
1
known unknown
0.6
x
2
1
=
0.6mol x
• 2 x = 0.6mol
•
• x = 0.3mol
ÿ 2 H2O
2
Chemistry R: Form TR7.13A
Test Review 7
TEST 7 REVIEW
ENERGY
Calculating Joules. When you heat a solid, it’s temperature generally goes up.
There is a relationship between heat and temperature, but they are not the same
thing. It would take a lot more energy to heat up the ocean than to warm a cup of
tea. The ocean has a larger mass. It has many more molecules to share energy with.
Mass is not the only thing that influences the way the temperature changes in
response to heat. When the same sun beats down on the beach, the sand gets a lot
hotter than the water. Water has a higher heat capacity than sand. The relationship
between mass, temperature change, specific heat, and energy are shown to the right.
Specific Heat. Some substances are more resistant to temperature change than
others. They have a higher specific heat. The equation for determining specific heat
is shown to the right
Temperature scales. The Celsius scale is based on water. The freezing point of
water is 0EC, while the boiling point of water is 100EC. The Kelvin scale is based
on the Celsius scale with the zero at absolute zero. Absolute zero is the lowest
possible temperature. It is the temperature at which particles of matter stop moving.
K = EC + 273 and EC = K – 273
Page 2
Q = mCp∆T
Q = heat (J)
m = mass in grams
∆T = change in temperature [∆T = Tf – Ti]
Tf = final temperature
Ti = starting temperature
Cp = 4.18 J/gEC for water
Cp =
Q
m∆ T
Q = joules;
m = mass in grams
∆T = change in temperature [∆T = Tf – Ti]
Tf = final temperature (EC)
Ti = starting temperature (EC)
Cp = specific heat (J/gEC)
PHASES OF MATTER
Comparing Solids, Liquids, and Gases. Solids are substances with a definite shape and volume. The particles of solids vibrate about fixed
positions, held in place by large forces of attraction. Liquids have a definite volume, but their shape is determined by their container. The
particles of a liquid roll and slide over each other. Both the shape and volume of a gas are determined by the container. This is because
the particles move independently, and spread out to fill the container. Gases are mostly empty space, and they can be compressed.
Kinetic Molecular Theory. Matter is composed of particles that are in constant motion (kinetic energy). There are forces of attraction
between particles that depend on the distance between the particles. The further apart the particles are, the smaller the forces of attraction
between them are. The higher the temperature (average kinetic energy) is, the faster the particles move. The Kinetic Molecular Theory
explains the phases. In solids the forces of attraction between particles are larger than in other phases. As a result, the particles are held
relatively close together in fixed positions, vibrating back and forth. Therefor the shape and volume are not determined by the container.
In liquids the forces of attraction between particles are moderate compared to other phases. The particles can move from place to place
but cannot separate from each other and move independently, so they roll and slide over each other. The particles are pulled downhill by
gravity causing the liquid to seek its own level, so the shape is determined by the container but the volume is not. In gases the forces of
attraction between particles are weaker than in other phases. The particles can move from place to place independently of each other
because they do NOT attract or repel each other. The particles are relatively far apart. The volume of the particles is small compared to
the space between them. Gases tend to spread out to fill their container. Therefor both the shape and volume are determined by the
container.
PHASE CHANGES
Heating a substance in a given phase causes the temperature to increase. Increasing the temperature
causes particles to move faster and collide harder. This causes the particles to rebound harder moving
them further apart. Larger distances between particles weakens the forces of attraction between them.
When the forces of attraction are weak enough, the distance between the particles increases markedly
and the phase changes. As a result, a solid melts, and a liquid evaporates. The reverse happens when
a substance cools, so a gas condenses, and a liquid freezes.
Phase Diagram. A phase diagram shows phases of a substance in a closed system as a function of
temperature and pressure. The points on the phase diagram are [a] the triple point where all three
phases of mater coexist; [b] the critical temperature above which vapor cannot be liquefied no matter
what pressure is applied; [c] the critical pressure, the pressure required to form a liquid at the critical
temperature; and [d] the critical point defined by the critical temperature and pressure.
Phase diagram for water
Chemistry R: Form TR7.13A
Test Review 7
TEST 7 REVIEW
Page 3
Answer the questions below by circling the number of the correct response
1. When the equation H2 + N2 ! NH3 is completely balanced using
smallest whole numbers, the sum of all the coefficients will be (1) 6
(2) 7 (3) 3 (4) 12
15. What is the mass of 3.0 × 1023 atoms of neon
[NOTE: 1 mol = 6.0 × 1023 particles]? (1) 1.0 g (2) 10. g (3) 0.50 g
(4) 20. g
2. When the equation H2 + Fe3O4 ! Fe + H2O is completely balanced
using smallest whole numbers the coefficient of H2 would be (1) 1
(2) 2 (3) 3 (4) 4
16. Which represents the greatest mass of chlorine (1) 1 mole of
chlorine (2) 1 atom of chlorine (3) 1 gram of chlorine (4) 1 molecule
of chlorine
3. When the equation __C2H4 + __O2 ! __CO2 + __H2O is correctly
balanced, using smallest whole-numbered coefficients, the sum of
all the coefficients is (1) 16 (2) 12 (3) 8 (4) 4
17. What is the total mass of iron in 1.0 mole of Fe2O3? (1) 160 g
(2) 72 g (3) 112 g (4) 56 g
4.
5.
When the equation NH3 + O2 ! HNO3 + H2O is completely balanced
using smallest whole numbers, the coefficient of O2 would be (1) 1
(2) 2 (3) 3 (4) 4
When the equation __Na(s) + __H2O(R) ! __NaOH(aq) + __H2(g)
is correctly balanced using smallest whole numbers, the coefficient
of the water is (1) 1 (2) 2 (3) 3 (4) 4
6.
Given the reaction: N2(g) + 3H2(g) W 2NH3(g)
What is the ratio of molecules of H2(g) consumed to molecules of
NH3(g) produced? (1) 1:2 (2) 2:3 (3) 3:2 (4) 6:6
7.
When the equation __Al(s) + __O2(g) ! __Al2O3(s) is correctly
balanced using the smallest whole numbers, the coefficient of Al(s)
is (1) 1 (2) 2 (3) 3 (4) 4
8.
Given the unbalanced equation:
Al2(SO4)3 + Ca(OH)2 ! Al(OH)3 + CaSO4., when the equation is
completely balanced using the smallest whole-number coefficients,
the sum of the coefficients is (1) 15 (2) 9 (3) 3 (4) 4
9.
A compound contains 0.5 mole of sodium, 0.5 mole of nitrogen, and
1.0 mole of hydrogen. The empirical formula of the compound is
(1) NaNH
(3) NaNH2
(2) Na2NH
(4) Na(NH)2
10. Which quantity is equivalent to 39 grams of LiF? (1) 1.0 mole
(2) 2.0 moles (3) 0.30 mole (4) 1.5 moles
11. What is the total number of molecules contained in 0.50 mole of O2
at STP [NOTE: 1 mol = 6.0 × 1023 particles]? (1) 6.0 × 1023
(2) 4.5 × 1023 (3) 3.0 × 1023 (4) 1.5 x 1023
12. At STP, what mass of CH4 has the same number of molecules as 64
grams of SO2? (1) 16 g (2) 32 g (3) 64 g (4) 128 g
13. What is the total number of moles contained in115 grams of
C2H5OH? (1) 1.00 (2) 1.50 (3) 3.00 (4) 2.50
14. How many moles of water are contained in 0.250 mole of
CuSO4•5H2O? (1) 1.25 (2) 40.0 (3) 4.50 (4) 62.5
18. What is the mass, in grams, of 1.0 mole of (NH4)2S? (1) 50. (2) 54
(3) 64 (4) 68
19. What is the gram atomic mass of the element chlorine? (1) 17 g
(2) 35 g (3) 52 g (4) 70. g
20. The mass in grams of 2.00 mole of CaSO4•2H2O is (1) 172 g
(2) 344 g (3) 136 g (4) 118 g
21. The gram molecular mass of CO is the same as the gram molecular
mass of (1) CO2 (2) C2H4 (3) SO2 (4) C3H8
22. Given the reaction: N2(g) + 3H2(g) W 2NH3(g), what is the ratio of
moles of H2(g) consumed to moles of NH3(g) produced? (1) 1:2
(2) 2:3 (3) 3:2 (4) 6:6
23. Given the reaction: (NH4)2CO3 ! 2NH3 + CO2 + H2O, what is the
minimum amount of ammonium carbonate that reacts to produce 1.0
mole of ammonia? (1) 0.25 mole (2) 0.50 mole (3) 17 moles
(4) 34 moles
24. According to the equation HCl + NaOH ÿ NaCl + H2O, the total
number of moles of HCl that can be neutralized by 2.0 moles of
NaOH is (1) 1.0 (2) 2.0 (3) 36 (4) 72
25. Which temperature represents absolute zero? (1) 0 K (2) 0EC
(3) 273 K (4) 273EC
26. At which temperature does a water sample have the highest average
kinetic energy (1) 0EC, (2) 100EC, (3) 0 K, (4) 100 K
27. When 84 joules of heat is added to 2.0 gram of water at 15EC, the
temperature of the water increases to (1) 5.0EC, (2) 15EC,
(3) 25EC, (4) 50. 0 C
28. Which Kelvin temperatures represent, respectively, the normal freezing
point and the normal boiling point of water? (1) 0 K and 273 K (2) 0 K
and 100 K (3) 100 K and 273 K (4) 273 K and 373 K
29. How many joules of heat energy are released when 50 grams of
water are cooled from 70EC to 60EC? (1) 42 joules (2) 209 joules
(3) 2090 joules (4) 4,180 joules
Chemistry R: Form TR7.13A
Test Review 7
TEST 7 REVIEW
Page 4
30. The number of joules needed to raise the temperature of 10 grams
of' water from 20EC to 30EC is (1) 42, (2) 84, (3) 418, (4) 167
45. Which substance readily sublimes at room temperature?
(1) H2O(R) (2) O2(g) (3) Fe(s) (4) CO2(s)
31. A 5-gram sample of water is heated and the temperature rises from
10EC to 15EC. The total amount of heat energy absorbed by the
water is (1) 105 J, (2) 84 J, (3) 63 J, (4) 21 J
46. Which change of phase represents sublimation?
(1) H2O(g) ÿ H2O(R) (2) H2O(R) ÿ H2O(s) (3) CO2(s) ÿ CO2(g)
(4) CO2(s) ÿ CO2(R)
32. At which temperature would the molecules in a one gram sample of
water have the lowest average kinetic energy? (1) 5EC (2) –100EC
(3) 5 K (4) 100 K
47. Which change of phase is exothermic? (1) gas to liquid (2) solid to
liquid (3) solid to gas (4) liquid to gas
42. Which of the following can be compressed under pressure?
(1) I2(s) (2) I2(R) (3) I2(g) (4) I2(aq)
43. Which 1.5-liter sample of salt does NOT take the shape of its
container? (1) NaCl(s) (2) NaCl(R) (3) NaCl(g) (4) NaCl(aq)
44. A 25.0 mL sample of water is poured from a 50.0 mL graduated
cylinder to a 100.0 mL graduated cylinder. The volume of the water
(1) increases, (2) decreases, (3) remains the same.
Answers
41. Which of the following has the strongest forces of attraction?
(1) CO2(s) (2) CO2(R) (3) CO2(g) (4) CO2(aq)
3
1
3
1
3
4
3
1
2
3
2
40. Which 5.0-milliliter sample of NH3 will take the shape of and
completely fill a closed 100.0-milliliter container? (1) NH3(s)
(2) NH3(R) (3) NH3(g) (4) NH3(aq)
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
39. The molecules of which substance have the highest average kinetic
energy? (1) He(g) at 0EC (2) CO2(g) at 20EC (3) HCl(g) at 40EC
(4) N2(g) at 60EC
3
4
3
3
1
3
1
2
1
1
3
2
4
38. If 4 grams of water at 1EC absorbs 33.6 joules of heat, the
temperature of the water will change by (1) 1 CE 2) 2 CE (3) 3 CE
(4) 4 CE
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
37. Which Kelvin temperature is equal to –33EC? (1) –33 K (2) 33 K
(3) 240 K (4) 306 K
1
2
1
3
4
2
2
2
3
2
2
1
2
36. When 5 grams of water at 20EC absorbs 10 joules of heat, the
temperature of the water will be increased by a total of (1) 0. 5 CE
(2) 2 CE (3) 10 CE (4) 50 CE
50. The temperature at which a substance can exist as a solid, liquid,
and gas simultaneously is the (1) melting point, (2) triple point,
(3) boiling point, (4) critical point.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
35. How many kilojoules of heat are needed to raise the temperature of
500. grams of water from 10.0EC to 30.0EC? (1) 41,800 J
(2) 104500 J (3) 209,000 J (4) 167,200 J
49. A substance sublimes at standard temperature and pressure. What
could be done to cause the substance to melt? (1) increase the
temperature (2) decrease the temperature (3) increase the
pressure (4) decrease the pressure.
1
4
3
2
2
3
4
2
3
4
3
1
4
34. The temperature of a substance changes from -173EC to 0EC. How
many Kelvin degrees does this change represent? (1) 100. (2) 173
(3) 273 (4) 446
48. Which sample contains particles arranged in regular geometric
pattern? (1) CO2(R) (2) CO2(s) (3) CO2(g) (4) CO2(aq)
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
33. How many kilojoules of heat energy are absorbed when 100 grams
of water is heated from 20EC to 30EC? (1) 4180 J (2) 41,800 J
(3) 418,000 J (4) 418 J