Unit 9 Packet pdf

Transcription

Unit 9 Packet pdf

Name: __________________________
Period: ___________
Unit 9 Packet – Stoichiometry 2
Packet Contents Sheet (This Page)
Unit 9 Objectives
Worksheet 1- Gases Again
Worksheet 2
Gas Stoichiometry Practice/ Ideal Gas Law Practice
Worksheet 3- Molar Concentration (2 pages)
Molarity Practice Problems
Notes on H
Worksheet 4
Unit 9 Study Guide
DO NOT, under any circumstances, throw this away!
This packet MUST be saved for the final exam.
Modeling Chemistry Unit 9 Packet
Page | 1
Unit 9 – Stoichiometry II - Objectives
Students can derive and use the Ideal Gas Law to determine an unknown pressure, quantity,
volume, or temperature. They will be able to use balanced chemical equations and quantity of a
reactant or product to calculate moles, mass, and chemical potential energy. Students will also
be able to calculate and use partial pressures within a mixture.
Scale
Score
Score 4
Comment
Without any major errors, students can independently:
 Students can apply laboratory data to derive and use the Ideal Gas Law to
determine an unknown pressure, quantity, volume, or temperature. They
will be able to use balanced chemical equations and quantity of a reactant or
product to calculate moles, mass, and chemical potential energy. Students
will also be able to calculate and use partial pressures within a mixture.
Score 3
Without any major errors, students can independently:
 Students can derive and use the Ideal Gas Law to determine an unknown
pressure, quantity, volume, or temperature. They will be able to use
balanced chemical equations and quantity of a reactant or product to
calculate moles, mass, and chemical potential energy. Students will also be
able to calculate and use partial pressures within a mixture.
Score 2
With one or two major errors, students can independently:
 Students can understand how to use the Ideal Gas Law to determine an
unknown pressure, quantity, volume, or temperature. They will be able to
understand the relationship between balanced chemical equations and
calculations of moles, mass, and chemical potential energy. Students will
also be able to calculate and use partial pressures within a mixture.
Score 1
With help from the teacher, students can:
Score 0
Even with the teachers help, students show no understanding or ability to:
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Name
Date
Pd
Chemistry – Unit 9
Worksheet 1 – Gases Again
1. A can of spray paint contains nitrogen gas as the propellant. The pressure of the
gas is 3.5 atm when the temperature is 20˚C. The can is left in the sun, and the
temperature of the gas increases to 50˚C. What is the pressure in the can?
2. A 90.0 mL volume of helium was collected under a pressure of 740. mmHg. At
what volume would the pressure of this gas be 700. mm Hg? Assume
temperature is constant.
3. A small bubble rises from the bottom of a lake, where the temperature is 8˚C and
the pressure is 6.4 atm, to the water’s surface, where the temperature is 25˚C
and pressure is 1.0 atm. Calculate the final volume (in mL) of the bubble if its
initial volume was 2.1 mL.
4. Three gases are mixed in a 1.00 L container. The partial pressure of CO2 is 250.
mm Hg, N2 is 375 mm Hg, and He is 125 mm Hg. What is the pressure of the
mixture of gases?
5. What are the percentages, by moles, of the gases in the above mixture?
Page | 3
6. Our atmosphere is a mixture of gases (roughly 79% N2, 20% O2 and 1% Ar).
What is the partial pressure (in mm Hg) of each gas at standard pressure?
7. A mixture of He and O2 gases is used by deep-sea divers. If the pressure of the
gas a diver inhales is 8.0 atm, what percent of the mixture should be O2, if the
partial pressure of O2 is to be the same as what the diver would ordinarily
breathe at sea level?
8. When you found the density of carbon dioxide gas, you collected the gas by
displacing water in a bottle. The gas you collected was a mixture of CO2 and
H2O vapor. If, on the day of the lab, the room pressure were 730 mm Hg and
the partial pressure of water vapor were 21 mm Hg, what would be the partial
pressure of the carbon dioxide gas? What fraction of the mixture was CO2?
9. Suppose that when you reacted the zinc with the hydrochloric acid, you collected
the hydrogen gas by water displacement. If the pressure in the room were 735
mm, and the partial pressure of the water were 22mm Hg, what would be the
partial pressure of the hydrogen gas? If the volume at this pressure were 25.0
mL, what would be the volume of the hydrogen gas alone at standard pressure?
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Name
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Chemistry – Unit 9 Worksheet 2
1. What volume does 16.0 g of O2 occupy at STP?
2. A mixture contains 5.00 g each of O2, N2, CO2, and Ne gas. Calculate the
volume of this mixture at STP
3. A 250 mL flask of hydrogen gas is collected at 763 mm and 35˚C by
displacement of water from the flask. The vapor pressure of water at 35˚C is
42.2 mmHg. How many moles of hydrogen gas are in the flask?
4. When calcium carbonate is heated strongly, carbon dioxide gas is evolved.
CaCO3(s) –––> CaO(s) + CO2 (g)
If 4.74 g of calcium carbonate is heated, what volume of CO2 (g) would be
produced when collected at STP?
Page | 5
5. Zinc metal reacts vigorously with chlorine gas to form zinc chloride. What
volume of chlorine gas at 25˚C and 1.00 atm is required to react completely with
1.13 g of zinc?
6. Consider the following reaction:
P4(s) + 6 H2 (g) ––> 4 PH3 (g)
What mass of P4 will completely react with 2.50 L of hydrogen gas, at 0˚C and
1.50 atm pressure?
7. If water is added to magnesium nitride, ammonia gas is produced when the
mixture is heated.
Mg3N2(s) + 3H2O(l) ––> 3 MgO + 2NH3(g)
If 10.3 g of magnesium nitride is treated with water, what volume of ammonia
gas would be collected at 20˚C and 0.989 atm?
8. Nitrogen gas and hydrogen gas combine to produce ammonia gas (NH3). What
volume of hydrogen gas at 25˚C and 735 mm is required for the complete
reaction of 10.0g of nitrogen?
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Name
Date
Pd
Gas Stoichiometry Practice
For all of these problems, assume that the reactions are being performed at STP.
1. Calcium carbonate decomposes at high temperatures to form carbon dioxide
and calcium dioxide:
CaCO3(s)  CO2(g) + CaO(s)
How many grams of calcium carbonate will I need to form 3.45 liters of carbon
dioxide?
2. Ethylene burns in oxygen to form carbon dioxide and water vapor:
C2H4(g) + 3 O2(g)  2 CO2(g) + 2 H2O(g)
How many liters of water can be formed if 1.25 liters of ethylene are consumed
in this reaction?
3. When chlorine is added to acetylene, 1,1,2,2-tetrachloroethane is formed:
2Cl2(g) + C2H2(g)  C2H2Cl4(l)
How many liters of chlorine will be needed to make 75.0 grams of C2H2Cl4?
Page | 7
Name
Date
Pd
Ideal Gas Law Practice
Solve the following problems using the ideal gas law.
1. How many moles of gas does it take to occupy 120 liters at a pressure of 2.3
atmospheres and a temperature of 340 K?
2. If I have a 50 liter container that holds 45 moles of gas at a temperature of
200C, what is the pressure inside the container?
3. It is not safe to put aerosol canisters in a campfire, because the pressure
inside the canisters gets very high and they can explode. If I have a 1.0 liter
canister that holds 2 moles of gas, and the campfire temperature is 1400C,
what is the pressure inside the canister?
4. How many moles of gas are in a 30 liter scuba canister if the temperature of
the canister is 300 K and the pressure is 200 atmospheres?
5. I have a balloon that can hold 100 liters of air. If I blow up this balloon with
3 moles of oxygen gas at a pressure of 1 atmosphere, what is the temperature
of the balloon?
Page | 8
Name
Date
Pd
Unit 9 Worksheet 3: Molar Concentration
Part A: Describing Molar Concentration
1. Sodium chloride was dissolved in water to produce a 1.5M solution.
Explain what this concentration tells us about the NaCl solution.
How might a chemist use this ratio?
2. A 45.3 g sample of potassium nitrate is dissolved in enough water to make
225 mL of solution. Determine the molar concentration of the potassium
nitrate.
3.
Find the molarity of a solution made from 275 g of CuSO4 dissolved in enough
water to make 4.25 L.
4. An alcoholic iodine solution (“tincture” of iodine) is prepared by dissolving 5.15 g
of iodine crystals in enough alcohol to make a volume of 225 mL. Calculate the
molarity of iodine in the solution.
5. What final volume would be needed in order to prepare a 0.25 M NaCl solution
from 5.2 g of NaCl (s)?
Page | 9
6. Draw a particle diagram of each of these ionic substances in solution. Then
calculate the molarity of each ion present in each of the following solutions.
a. 0.25 M AlCl3
b. 0.375 M Na2CrO4
c.0.0020 Ca(OH)2
d. 0.103 M Na3PO4
7. How many grams of silver nitrate are needed to prepare 250 mL of standard
0.100 M silver nitrate solution?
8. If 10.0 g of AgNO3 is available, find the volume needed to prepare a 0.25 M
AgNO3 solution.
9. Concentrated hydrochloric acid is made by pumping hydrogen chloride gas into
distilled water. If concentrated HCl contains 439 g of HCl per liter, what is the
molarity?
Page | 10
Part B: Molar Concentration and Stoichiometry
10. How many moles of lead(II) hydroxide (solid) can be formed when 0.0225L of
0.135 M Pb(NO3)2 solution reacts with excess sodium hydroxide? (Hint: Use a
BCA table).
11. Barium nitrate reacts with aqueous sodium sulfate to produce solid barium
sulfate and aqueous sodium nitrate. Abigail places 20.00 mL of 0.500 M
barium nitrate in a flask. She has a 0.225M sodium sulfate solution available.
What volume of this solution must she add to her flask of barium nitrate so she
has no excess reactant left over? (Use a BCA table to answer).
12. Calcium chloride (aq) reacts with sodium carbonate (aq) to from solid calcium
carbonate and aqueous sodium chloride. Determine the volume of a 2.00 M
Calcium chloride solution would be needed to exactly react with 0.0650 L of 1.50
M Na2CO3. (Use BCA!)
Page | 11
Name
Date
Pd
Molarity Practice Problems
1. How many grams of potassium carbonate are needed to make 200 mL of a
2.5 M solution?
2. How many liters of a 4 M solution can be made using 100 grams of lithium
bromide?
3. What is the concentration of an aqueous solution with a volume of 450 mL
that contains 200 grams of iron (II) chloride?
4. How many grams of ammonium sulfate are needed to make a 0.25 L
solution at a concentration of 6 M?
5. What is the concentration of a solution with a volume of 2.5 liters
containing 660 grams of calcium phosphate?
6. How many grams of copper (II) fluoride are needed to make 6.7 liters of a
1.2 M solution?
Page | 12
7. How many liters of a 0.88 M solution can be made with 25.5 grams of
lithium fluoride?
8. What is the concentration of a solution with a volume of 660 mL that
contains 33.4 grams of aluminum acetate?
9. How many liters of a 0.75 M solution can be made with 75 grams of lead
(II) oxide?
10. How many grams of manganese (IV) oxide are needed to make 5.6 liters
of a 2.1 M solution?
11. What is the concentrarion of a solution with a volume of 9 mL that
contains 2 grams of iron (III) hydroxide?
12. How many liters of a 3.4 M isopropanol solution can be made with 78
grams of isopropanol (C3H8O)?
13. What is the concentration of a solution with a volume of 3.3 mL that
contains 12 grams of ammonium sulfite?
Page | 13
Chemistry – Unit 9 Notes on ∆H
The Modeling approach stresses representing structure in systems or processes
several ways. We want you to be able to represent energy changes in chemical
reactions in multiple ways.
Consider the reaction in which methane burns in air to produce carbon dioxide
and water. The balanced equation for this reaction is
CH4 + 2 O2  CO2 + 2 H2O
Experiments show that when one mole of CH4 is burned, 890 kJ are released.
There are several ways we can represent this information.
1. Write the chemical equation including the energy term. Since energy is
released, we regard it as a product of the reaction.
CH4 + 2 O2  CO2 + 2 H2O + 890 kJ
We are now quantifying the treatment of chemical potential energy we began in
unit 5.
Sample question: What mass of oxygen gas is consumed when 35 kJ are
released in the reaction above?
2 molesO2
32 g
35 kJ 

 2.5 gO2
890 kJ
1mole
2. Sketching an energy bar graph for the reaction.

Note in this representation, we show that chemical potential energy of the
system decreases as the atoms are rearranged to form new molecules. The
thermal energy increases (system gets hotter) as energy is conserved.
Eventually, the system will lose energy to the cooler surroundings.
3. Write the energy term using ∆H notation.
The reaction is written: CH4 + 2 O2  CO2 + 2 H2O
∆H = –890 kJ
The negative sign indicates that the system loses chemical potential energy. It
is as if you made a withdrawal from the bank, lowering your account balance.
Page | 14
4. This reaction is said to be exothermic because eventually energy is transferred
from the system to the surroundings.
Next, you can show the various ways to represent an endothermic reaction.
Experimental evidence has shown that the chemical reaction:
H2 + Br2  2 HBr requires 72.8 kJ of energy to proceed. Your goal is to
represent this reaction three different ways:
1. by writing a balanced equation with the energy term in the equation.
2. by completing an energy bar graph diagram, showing how Eth and Ech change
in the system. Will energy eventually flow into or out of the system? Why?
3. by using the ∆H notation to describe the energy.
Page | 15
Name
Date
Pd
Chemistry – Unit 9 Worksheet 4
1. How many kJ of heat will be released when 4.72 g of carbon react with excess
oxygen gas to produce carbon dioxide?
C + O2  CO2
∆Hº = –393.5 kJ
2. How much heat should be transferred when 38.2 g of liquid bromine reacts with
excess hydrogen gas to form hydrogen bromide? Is the heat being transferred
from the system to the surroundings or from the surroundings to the system?
H2 + Br2  2 HBr
∆Hº = 72.80 kJ
3. How many kJ of heat would you expect to be transferred when 6.44 g of sulfur
react with excess oxygen gas to produce sulfur trioxide? Is this reaction
endothermic or exothermic?
2 S + 3 O2  2 SO3
∆Hº = –791.4 kJ
4. Nitrogen gas and oxygen gas can combine to produce nitric oxide, NO. If such a
reaction absorbs 88.0 kJ of heat from the surroundings, how many grams of
nitrogen gas do you predict were consumed in the reaction?
N2 + O2  2 NO
∆Hº = 180 kJ
Page | 16
5. Ammonia gas combines with excess oxygen gas to produce nitric oxide and
water. If 256 kJ of energy were released in such a reaction, how many grams of
ammonia gas were reacted?
4 NH3 + 5 O2  4 NO + 6 H2O
∆Hº = – 1170 kJ
6. Carbon in the form of graphite combines with excess hydrogen gas to form
benzene, C6H6. In the following reaction 3.95 kJ of heat were transferred.
Calculate the grams of graphite reacted. Is the reaction endothermic or
exothermic?
6C (graphite) + 3 H2  C6H6
∆Hº = 49.03 kJ
7. How much heat will be released if 30.0 g of octane (C8H18) is burned in excess
oxygen?
C8H18 + 12 1/2 O2  8 CO2 + 9 H2O
∆H = –5483.4 kJ
How much heat would be released by burning one gallon of octane? The density
of octane is 0.703g/mL. 1 gallon = 3.79 liters.
1. 155 kJ
5. 14.9 g
2. 17.4 kJ
6. 5.80 g
3. 79.5 kJ
4. 13.7 g
7. 1440 kJ, 128,000 kJ
Page | 17
Chemistry – Unit 9 Review
Molar volume and gas stoichiometry
1. A mixture contains 8.00 g each of O2, CO2, and SO2 at STP. Calculate the
volume of this mixture. Which of the gases would exert the greatest pressure
and why?
22.4L
Molar volume =
1mole

2. Nitrogen gas and hydrogen gas combine to produce ammonia gas (NH3). What
volume of hydrogen gas at STP would be required to react with 10.0 g of nitrogen
gas?
3. Consider the following reaction: P4(s) + 6 H2(g)  4 PH3(g)
What volume of hydrogen gas at 25C and 0.981 atm is required to react
completely with 2.51 g of P4 ?
L  atm
PV  nRT
R  0.0821
mole  K


Page | 18
Molar concentration
4. What mass of Na2CO3 is needed to prepare 1.25 L of a 0.75M solution?
Mass stoichiometry
5. When potassium carbonate reacts with hydrogen chloride, the products are
potassium chloride, carbon dioxide and water. What mass of hydrogen chloride
is needed to completely react with 14.8 g of potassium carbonate?
Representing reactions
6. Nitric oxide (NO) reacts with oxygen gas to produce nitrogen dioxide. In the box
at left represent a mixture containing 8 molecules of NO and 6 molecules of O2.
In the box at right represent the system after the reaction had gone to
completion. Be sure to provide a key.
––>
a. Write the balanced equation for the reaction.
b. Which is the limiting reactant?
c. How many molecules of the xs reactant remain?
Page | 19

Unit 9 Packet pdf

Transcription

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