Download Chemistry 20 – Unit 2 – Gases – FITB Notes Topic A

Chemistry 20 – Unit 2 – Gases – FITB Notes
General Outcome:
I. I can _________________________________________________________________________
Topic A – Characteristics of Gases
Specific Outcomes:
I. I can _________________________________________________________________________
_____________________________________________________________________________
We use technologies that were designed with the knowledge of the visible characteristics
(___________) of gases
ex. SCUBA equipment, hot air balloons, jackhammers
Gases have several distinct macroscopic (visible with the unaided eye) properties:
1. Gases are ____________
i.e. ↑ pressure = ↓ volume
2. Gases ________ as temperature increases
i.e. ↑ temperature = ↑ volume (soft container)
↑ temperature = ↑ pressure (rigid)
3. Gases have _______________________ (viscosity)…allows them to escape quickly
through small openings (leak)
4. Gases have low __________
5. Gases mix evenly and completely; they are all __________ (gases mix well!)
6. Gases have no shape or volume, they ________________ of the container they are in by
expanding or compressing
MEMORIZE these properties; they represent the ___________ properties of gases!
Topic B – Particle Theory
Specific Outcomes:
I. I can _________________________________________________________________________
_____________________________________________________________________________
We need models to describe how gases behave on the ____________ (particle) level
The kinetic molecular theory says that all particles are in _______ at all times
KMT focuses on particle motion, which cannot be seen with the unaided eye (_________)!
An ideal gas (which is hypothetical) is defined by the following characteristics:
1. The gas molecules are in constant ________ motion, where they move in a straight line
until they _______ with another particle or the wall of the container
2. The gas molecules are “______________” (they have mass but __________, and act
like point spheres)
3. The only interaction between molecules of the gas and container are ______
collisions…collisions where kinetic energy is __________, not lost!
Topic C – Ideal Gas vs. Real Gas
1
Specific Outcomes:
I. I can _________________________________________________________________________
_____________________________________________________________________________
_____ gases correspond perfectly to equations
_____ gases do not behave this way…however, they are behave much like ideal gases!
For ideal gases we assume that there are no _____________ attractions (LD, DD, HB) at all
between molecules of gas
In real gases, however, there are ___________ between molecules of gas
We don’t have to worry about considering this in our calculations because at standard __ and __
conditions the ideal gas molecules are:
1. _____________ (lots of space)
2. are moving very ________ (high energy)
3. not interacting (__________________) much with each other
Real gases behave like ideal gases at:
____ temperatures (fast moving)
____ pressures (very far apart)
Real gases deviate from ideal gas behaviour at:
__________ temperatures (moving very slowly)
__________ pressures (molecules close together)
Real gases also deviate from ideal gas behaviour if molecules have:
_______ size (more electrons)
_______ shape (branching, etc.)
Topic D – Atmospheric Pressure
Specific Outcomes:
I. I can _________________________________________________________________________
_____________________________________________________________________________
Although gas molecules in the atmosphere have little _____, Earth’s gravitational pull keeps
them near the surface (except H, He)
Atmospheric pressure is the force that a column of air exerts on a particular area on the Earth’s
surface (force per ________)
Atmospheric pressure is exerted _________ in all directions to the same extent
Air is less compressed as altitude increases… so _____ pressure is exerted higher up
Pascal and Perier used Hg(l) to prove that atmospheric pressure ________ with altitude
The work of Pascal, Perier and Torricelli all led to the development of the mercury _________
There are several different units used to measure pressure:
millimetres of mercury (______)
atmosphere (____)
kiloPascal (____)
Pascal (Pa) 1 ____ = 1000 ____ (optional)
bar 1 ____ = 100 ____ (optional)
You will be using the standard unit of kPa in gas law calculations and therefore you must be able
to convert ______ and _____ to kPa
Memorize the following standard pressures:
To convert other units of pressure to kPa, set up a ______
2
ex. 1:
Convert 650 mmHg to kPa.
ex. 2:
Convert 2.5 atm to kPa.
Topic E – Boyle’s Law
Specific Outcomes:
I. I can _________________________________________________________________________
_____________________________________________________________________________
Robert Boyle studied the mathematical relationship between the pressure and volume of a gas at
________ temperature
_______ against the walls of a container is caused by collisions of the gas molecules with the
walls
As you _______ the volume of a contained gas, there is less room for the gas particles
A smaller volume means that the number of collisions ________
Container pressure is proportional to the number of collisions against the walls (more collisions
means a ______ pressure)
Boyle found a relationship between pressure and volume (MEMORIZE):
During an inhale, lung volume _________ to ______ pressure and draw in more air
Boyle’s Law – volume of a gas varies inversely with the pressure, at constant temperature and
mass (MEMORIZE):
ex. A balloon is filled with 30.0 L of helium gas at 100 kPa. What is the volume when the balloon
rises to an altitude where the pressure is only 25.0 kPa? (constant T)
ex. The pressure on 2.50 L of anesthetic gas is 100 kPa. If 6.25 L of gas is the required volume, what
pressure must it be under, assuming constant temperature?
Topic F – Law of Combining Volumes
Specific Outcomes:
I. I can _________________________________________________________________________
3
Gay-Lussac analyzed chemical _________ that involved gases
He studied the ________ of the gaseous reactants and products and concluded that the gases
combine in very simple ____________
The Law of Combining Volumes states: when gases react, the volumes of the gas reactants and
products (at constant temperature and pressure) are always in _______________________
ex. N2(g) + 3H2(g) 2NH3(g)
ex. What volume of nitrogen is used up if 100 mL of ammonia is formed in a composition reaction?
Topic G – Kelvin Temperature Scale
Specific Outcomes:
I. I can _________________________________________________________________________
When volume and temperature of a gas are graphed, the plot is ________ (as long as amount of
gas and pressure were constant)
It was also noticed that when these linear plots were extrapolated down to _____________, all
the lines converged at one point
The temperature when the volume of a gas is zero is ___________ (zero kinetic energy!)
Lord Kelvin (1848) suggested that this is the lowest possible temperature, _______________ (no
particle movement whatsoever!)
He established a new temperature scale which is called the ________ scale in his honour
“t” is used for temperature in ___
“T” is used for temperature in ___
-273.15°C = absolute zero = __ K
We use _______ (K), instead of Celsius, for calculations in chemistry:
ex.
Topic H – Charles’ Law
Specific Outcomes:
I. I can _________________________________________________________________________
_____________________________________________________________________________
Jacques Charles (and Gay-Lussac) noticed a relationship between the ___________ and _______
of a gas
As temperature __________, so did the kinetic energy of the gas molecules (because gas
particles move faster at _______ temperature!)
As the molecules move faster, they also exert higher _________ on the inside of the container
4
Gas volume will expand under this pressure until the pressure inside equals the outside
(____________) pressure
Charles’ Law – volume of a gas varies directly with the temperature, at constant pressure and
mass (MEMORIZE):
ex. A balloon was inflated at 27°C and has a volume of 4.0 L. If it is heated to 57°C, what is the new
volume? (assume constant P)
ex. A sample of gas occupies 6.8 L at 110°C. What will the final temperature be in °C when the
volume is decreased to 5.6 L?
Topic I – STP and SATP
Specific Outcomes:
I. I can _________________________________________________________________________
_____________________________________________________________________________
Two temperature and pressure conditions are on the back of your periodic table:
• STP (Standard Temperature, Pressure) conditions = __°C and ________ kPa
• SATP (Standard Ambient Temperature, Pressure) conditions = ___°C and ____ kPa
These two conditions will be used frequently
Remember to convert temperature to Kelvin!
Topic J – Combined Gas Law
Specific Outcomes:
I. I can _________________________________________________________________________
_____________________________________________________________________________
II. I can _________________________________________________________________________
_____________________________________________________________________________
III. I can _________________________________________________________________________
_____________________________________________________________________________
We can combine Boyle’s Law with Charles’ Law to get the Combined Gas Law:
ex. A weather balloon is filled with H2 (g) at 20°C and 100 kPa. It has a volume of 7.50 L. It rises to
an altitude where the air temperature is -36°C and the pressure is 28 kPa. What is the new
volume of the balloon?
5
Topic K – Ideal Gas Law
Specific Outcomes:
I. I can _________________________________________________________________________
_____________________________________________________________________________
II. I can _________________________________________________________________________
_____________________________________________________________________________
III. I can _________________________________________________________________________
_____________________________________________________________________________
Ideal Gas Law – A gas law that combines moles with P, V and T (on periodic table):
ex. A rigid steel vessel with a volume of 20.0 L is filled with nitrogen gas to a pressure of 20,000
kPa at 27°C.
a) How many moles of nitrogen does the vessel contain?
b) What is the mass of nitrogen?
ex. What is the volume of 10.8 mol of oxygen gas at 100.00 kPa and 15.5°C?
ex. What is the pressure exerted by 15.5 g of methane, CH4 (g), if it occupies a volume of 10.0 L at
25°C?
Topic L – Law of Partial Pressures
Specific Outcomes:
I. I can _________________________________________________________________________
_____________________________________________________________________________
Dalton’s law of partial pressures states that in a mixture of gases that do not ______
chemically, the total pressure is the _____ of the partial pressures of each individual gas:
ex. Two gases are pumped into a 32.0 L reaction vessel at 25.0°C, one after another. First, 6.20 mol
O2(g) is pumped in. Then 8.30 mol of H2(g) is added. What would the pressure gauge read after
each gas is pumped in?
6