GASES OBJECTIVES – PART TWO
The student will be able to:
Define effusion and diffusion.
Qualitatively describe rates of effusion/diffusion of various gases.
Compute relative rates of effusion/diffusion.
State the ideal gas equation (PV=nRT).
Use PV=nRT to solve problems.
Complete molar mass calculations involving gases.
Complete gas density calculations.
Describe the physical and chemical properties of carbon dioxide.
Describe the physical and chemical properties of hydrogen.
Describe the physical and chemical properties of oxygen.
Complete stoichiometry calculations involving gases.
Apply “Avogadro’s shortcut” to solve gas/gas stoichiometry problems.
THE IDEAL GAS EQUATION
(aka THE IDEAL GAS LAW)
1. State the ideal gas equation:
2. Common values for R:
A.
B.
c.
3. 3.4 moles of nitrogen was placed in a 10.0 L tank at 22oC.
the pressure inside the tank.
Compute
4. It is difficult to measure the volume of a balloon, but very easy to
measure temperature and pressure. Compute the volume of a balloon that
is known to contain 44 moles of hydrogen and is at .388 atm and -5.3oC.
5. A partially used tank of argon (V = 25L) is at 19oC and 18200 mm Hg.
How many moles of argon are in the tank?
6. Compute a value for R in ml*in Hg/(mol*K).
about gases at STP.
Hint: Use what you know
7. What mass of oxygen would be needed to create a pressure of 17.3 atm
in a 56 L tank at 31oC ?
8. A SCUBA diver's buoyancy control device (BCD) was inflated with 19.8g
of oxygen at a depth of 100 ft, where the pressure is 4.0 atm and the
temperature is 6oC. Compute the BCD's volume.
9. A welding company purchases oxygen by the kilogram. If the going
price is $10.50 per kilogram, what will it cost to fill twenty 30.0L
tanks to 2500psi on a 20.0oC day?
10. A clown filled 100 4.0L balloons with helium, on a warm (27oC),
fair(790 mm Hg) day. Find the moles of helium the clown used.
11. What mass of helium did the clown use?
12. If the clown's 25.0 L helium tank was at a pressure of 194.2 atm to
start, what pressure is it at after the balloons are filled?
13. Why should you be careful handling tanks of gases, whether the gas
is flammable (such as propane) or not (such as helium)?
PV=nRT, continued and extended
1. A welding tank contains 100L of oxygen at a pressure of 17atm
and 30 C. How many moles of oxygen is this?
2. What is the mass of the oxygen in the tank in the prior question?
3A. A scuba tank has a volume of 60 L. It is filled to a pressure of
3000psi at 20 C. How many moles of air does it hold?
3B. What is the partial pressure of oxygen in the tank?
3C. The tank is cooled to –10 C.
tank?
What is the pressure of the air in the
4. What pressure would be needed to compress 6.0mol of Ar to 10.0L at 10
C?
5A. An unknown gas occupies 1.2 L at 1.0 atm and 40C.
gas is this?
5B. The sample of gas has a mass of 2.2 g.
How many moles of
What is its molecular mass?
6A. A SCUBA tank holds 9.3L of air at a pressure of 2850 psi and a
temperature of 22 degrees Celsius. How many moles of gas does it
contain?
6B. Given that the "molar mass" of air is 29 g/mol, what mass of air is
in the SCUBA tank?
6C. Explain how the molar mass of AIR was calculated (and found to be 29
g/mol).
7A. A carbon dioxide fire extinguisher has a volume of 8.8L and is at a
pressure of 5.2 atm on a 20.0oC day. How many moles of CO2 would you
calculate that it contains?
7B. The same extinguisher actually contains 50 moles of carbon dioxide.
How can this be possible?
7C. Does carbon dioxide exhibit ideal behavior under these conditions?
GASES AND STOICHIOMETRY
1. Calculate the volume of dry hydrogen that can be formed at 21oC and
1.05atm from the reaction of excess hydrochloric acid and 2.44g of zinc.
2. Calculate the volume of dry hydrogen that can be formed at 17oC and
97.4kPa from the reaction of excess sulfuric acid and .714g of calcium.
3. 422ml of hydrogen was collected over water at 19.5oC and 104.4kPa
from the reaction of excess hydrochloric acid and iron. What mass of
iron reacted (forming iron(III) chloride)?
1. What mass of hydrogen peroxide would be needed to create 5.77L of dry
oxygen at 22.0oC and 790 mm Hg?
2. A .250 g marble chip was completely reacted with excess HCl. What
volume of dry carbon dioxide could be produced at 15oC and 750 mm Hg?
3. What mass of sodium bicarbonate was reacted with excess hydrochloric
acid if 12.1L of carbon dioxide was collected over water at 45oC and
.977atm?
4. What mass of CaC2 would be needed to produce acetylene to fill twenty
40.0L tanks at 25.0oC and 2500psi?
EFFUSION AND DIFFUSION OF GASES
1. Define the following:
Effusion
Diffusion
2. In each of the following pairs, circle the gas that diffuses
(effuses) more quickly:
He, Ne
O2, cO2
N2O, C2H6
nitrogen, neon
3. Compute the relative rates of diffusion of hydrogen and argon:
4. Compute the relative rates of effusion of carbon dioxide and
nitrogen:
5. Helium and oxygen are released in one corner of a room. In the
opposite corner is a detector. After 12 seconds the helium has reached
the detector. When will the oxygen reach the detector?
Gases:
Density, Molecular Mass, etc.
1. Determine the density of neon at 25oC and .723 atm.
2. Determine the density of chlorine at 327oC and 120.33 kPa.
3. 3.22g of an unknown gas was collected over water in a 1.00L container
at 34.5 oC and 755.2 Torr. Determine the molecular mass of this gas:
4. 1.91g of an unknown gas was collected over water at 34.5 oC and 755.2
Torr. The volume was 452.1 ml. Determine the molecular mass of this
gas:
AVOGADRO’S SHORTCUT
1. State Avogadro’s Principle:
2A. Avogadro’s Principle explains Gay-Lussac’s law of combining volumes
of gases. State this law:
2B. AND, these small whole numbers are the _________________ from the
chemical equation!
3. All of this leads to what we call ___________________ _______________
for gas stoichiometry problems. This shortcut only works if both of the
following are true:
A.
B.
For each of the following, indicate whether the problem is:
D = difficult = extended (or not even possible with the given info)
E = easy (Avogadro’s shortcut applies) (GO AHEAD AND SOLVE!)
1.
Si(s) + 2F2(g) ---------> SiF4(g)
_____ At constant conditions of 4.0 atm and 270o C, determine the volume
of fluorine needed to make 12.4 L of product.
_____ At constant conditions of 4.0 atm and 27o C, determine the volume
of silicon needed to make 12.4 L of product.
2.
2 S(s) + 3 O2 (g)
----> 2 SO3 (g)
_____ If 4.5 L oxygen reacts at 100.3 kPa and 23o C, what volume of SO3
is expected, at the same conditions.
_____ If 4.5 L sulfur reacts at 100.3 kPa and 23o C, what volume of SO3
is expected, at the same conditions.
EXTRA GAS PROBLEMS
Unit Test Preparation
1. Compute the pressure exerted by 1.45 moles of oxygen in a 3.44L tank
at a temperature of 29oC:
2. A balloon was filled with 43.2g of nitrogen at a temperature of
23.0oC and a pressure of 105.7 kPa. What is the volume of the balloon?
3. 245 ml of helium was collected over water at 25.0oC and 751 mm Hg.
What mass of helium was collected?
4. 15.2 mol of neon was placed in a 122L tank.
the neon exert a pressure of 7.88atm?
At what temperature will
5. 560.3 ml of an unknown gas was collected over water at 30.0oC and
.982atm. The mass of the collected gas was 1.75g. Determine the
molecular mass of this gas:
6. A SCUBA diver is going to be working at a depth of 33ft, where the
pressure is 2.00 atm. She breathes 15 times per minute, and has a
lung capacity of 4.00L. How long will her 25.0L SCUBA tank last if it
was filled to 200atm at a temperature of 30.0oC?
7. Determine the density of oxygen at 36oC and 92.4 kPa:
8. 6.94g of an unknown gas has a volume of 5.93L at 55oC and
420 mm Hg. Determine the molecular mass of this gas.
9. 45.4 ml of hydrogen was collected over water at 23 deg. C and 30.11
in. Hg. What mass of aluminum reacted with hydrochloric acid to form
this hydrogen?
10. What volume of dry carbon dioxide would be expected at 45 deg. C and
770.2 mm Hg, from the thermal decomposition of .234g of sodium
carbonate?
11. Determine the density of neon at 12 deg C and .997 atm.
12. Compute the volume 4.2 moles of nitrogen would be expected to have
at -200 deg C and 2.0 atm. The actual volume is 11 milliliters.
Explain.
13. An unknown gas a density of 3.4 g/L at 120 deg C and 740.9 mm Hg.
Determine the molecular mass of this gas.
Answers:
1. 10.5 atm,7940 Torr
2. 35.9 L
4. 770 K
5. 82.6 g/mol
6. 40.3 min.
8. 57.0 g/mol
9. .0328 g Al
10. .0569 L
12. 12.6 L (It’s a liquid!)
13. 113 g/mol
3. .0383g He
7. 1.15 g/L
11. .860 g/L
MORE EXTRA GAS PROBLEMS
ALSO REVIEW:
Kinetic Theory, Assumptions, The Laws, etc…
1. Determine the density of nitrogen at 150 deg C and 150.9 kPa.
2. Compute the volume 4.2 moles of nitrogen would be expected to have at
-200 deg C and 2.0 atm. The actual volume is 11 milliliters. Explain.
3. An unknown gas has a density of 1.5 g/L at 260 deg C and .855 atm.
Determine the molecular mass of this gas.
4. Compute the pressure exerted by 23.5 moles of oxygen in a 100L tank
at a temperature of 25oC:
5. A balloon was filled with 12.4g of oxygen at a temperature of 23.0oC
and a pressure of 720.4 mm Hg. What is the volume of the balloon?
6. 250 ml of hydrogen was collected over water at 22.0oC and 749.2 mm
Hg. What mass of iron reacted with HCl (forming ferric product) to
create this hydrogen?
7. 3.4 mol of neon was placed in a 22L tank.
the neon exert a pressure of 4.77 atm?
At what temperature will
8. 400.2 ml of an unknown gas was collected over water at 20.0oC and
1.03 atm. The mass of the collected gas was 1.22 g. Determine the
molecular mass of this gas:
9. Determine the density of ammonia (NH3) at 100oC and 2.44 atm:
10. 100.3 ml of hydrogen was collected over water at 27 deg. C and 29.87
in. Hg. What mass of zinc reacted with hydrochloric acid to form this
hydrogen?
11. What volume of dry carbon dioxide would be expected at 756.1 mm Hg
and 25oC, from the thermal decomposition of .0934g of lithium carbonate?
12. A sample of neon has a volume of 3.4 L at 44 deg C and 99.3 kPa.
Compute the volume at 22 deg C and 104.3 kPa.
13. At what temperature will a sample of argon occupy a volume of 23 L
if it has a volume of 17 L at 20 deg C? (P constant)
14. At what pressure will a sample of neon occupy a volume of 200 L if
it has a volume of 300 L at 2.80 atm? (T constant)
Answers:
4. 5.75 atm
8. 72.8 g/mol
12. 3.0 L
1. 1.20
5. 9.94
9. 1.36
13. 396
g/L
L
g/L
K
2. 12.5 L
3. 77 g/mol
6. .369 g Fe
7. 376 K
10. .00392 mol Zn
11. 31.1 ml
14. 4.20 L
DISTRICT GASES ASSESSMENT REVIEW
REVIEW:
etc…
Kinetic Theory, Assumptions, The Laws, Phases, Particle Motion,
1. Compute the pressure exerted by 12.5 moles of chlorine in a 55.7L
tank at a temperature of 259oC:
2. A balloon was filled with 5.99 mol of helium at a temperature of
21.0oC and a pressure of 99.7 kPa. What is the volume of the balloon?
3. .785 mol of oxygen was placed in a 7.99L tank.
will the neon exert a pressure of 8.65atm?
At what temperature
4. Compute the volume of a helium balloon at -11 degrees C. and .233
atm, if the balloon had a volume of 4500L when it was released at
.987atm and 25.0 degrees C.
5. If 3.55g of propane is burned at 170 degrees C and 77.4kPa, determine
the volume of dry carbon dioxide that should be expected. (Assume all
water is removed.)
_____ C3H8
+
_____ O2
---
_____ CO2
+
_____ H2O
6. Compute the pressure exerted by 23.5 moles of oxygen in a 100L tank
at a temperature of 25oC:
7. 5.66L of hydrogen was collected at 18.0oC and 765.2 mm Hg.
mass of lead reacted with HCl to create this hydrogen?
_____ Pb
+
_____ HCl
---
_____ PbCl4
+
_____ H2
What
DISTRICT GASES ASSESSMENT REVIEW – PAGE 2
REVIEW:
Kinetic Theory, Assumptions, The Laws, Phases, Particle Motion…
1. Compute the temperature at which 12.5 g of fluorine will exert a pressure of
217.1 kPa in a 10.5L tank:
2. Find the volume of a balloon filled with 18.22 mol of hydrogen at a
temperature of 17.0oC and a pressure of 765.2 mm Hg:
3. Compute the volume of a hydrogen weather balloon at -43 degrees C. and .188
atm, if the balloon had a volume of 1990L when it was released at 1.012atm and
31.0 degrees C.
4. List characteristics of each:
SOLID
LIQUID
GAS
5. 4.55g of 1ron was reacted with excess HCl.
is expected at 28.0oC and 752.3 Torr?
_____ Fe
+
_____ HCl
---
_____ FeCl3
What volume of hydrogen
+
_____ H2
6. If 14.56L of oxygen is consumed at 120 degrees C and 99.4kPa,
determine the mass of nonane (C9H20) that was burned.
_____ C9H20
+
_____ O2
---
_____ CO2
+
_____ H2O
7. Compute the pressure exerted by 112.6g of oxygen in a 42.9L tank at a
temperature of 117oC:
LAB – Molar Relationship of Hydrogen and Magnesium
PURPOSE:
The purpose of this lab is to examine the stoichiometric
relationship between magnesium and hydrogen.
BACKGROUND:
We will react magnesium with hydrochloric acid.
the complete, balanced equation:
Below, write
What type of reaction is this? __________________________________
PROCEDURE:
(Remember that we saw this procedure demonstrated.)
1. Fill a large container with water, so that it can come to room temperature.
2. Obtain the first three items of data from the instructor, and record in the
data table. Record all other measurements as taken.
3. Obtain a pre-cut piece of magnesium and carefully measure its length.
4. Also record observations of the magnesium, and continue recording
observations throughout the lab.
5. Fold the magnesium and wrap with copper wire, as demonstrated.
“tail” for later use.
Leave a
6. Prepare a ring stand and clamp to support the eudiometer during the
reaction.
7. Slightly tilt the eudiometer and add approximately 10ml of 3M hydrochloric
acid.
8. With the eudiometer still tilted, add water SLOWLY, so that it doesn’t mix
with the acid. Fill completely.
9. Insert the “caged” magnesium 3-4 cm into the eudiometer and wrap the tail
around the mouth of the eudiometer.
10. Place thumb or finger over the mouth of the tube and invert into the large
container of water. Place the eudiometer on the bottom, and clamp in place.
11. After the magnesium has completely reacted, tap the sides of the
eudiometer to release any gas bubbles.
12.
Read and record the volume.
13. Save the copper wire.
well.
Empty the other materials into the sink and rinse
DATA TABLE:
Mass of 1.000m Mg ________
Room Temperature ________
Length of Mg ________
Room Pressure _______
Mass of Mg reacted _______
Volume of hydrogen _______
Moles Mg reacted ________
Pressure Difference _______mm water
Moles of H2 predicted _______
ACTUAL Moles of H2 _______
Percent Yield _________
ANALYSIS:
1. While the reaction is running, complete the calculations for the first
column of the data table. ALL CALCULATIONS MUST BE IN LAB REPORT FORMAT!
2. After the lab, complete the calculations for the rest of the data table.
3. Compare the actual and expected yields.
4. Write a brief conclusion, including an IN DEPTH discussion of two possible
sources of error AND THEIR EFFECT on your final results.