CHAPTER SIX- GASES Flashcards
The most important gas in the atmosphere (to us) is _______, which constitutes about ______% of the atmosphere.
Oxygen; 21%
Of the elements on the periodic table, only a handful of exist as gases at room temperature. What are they?
H2, N2, O2, F2, Cl2 and the noble gases.
Another group of gases includes the oxides of the nonmetals on the upper right coercer of the periodic table, such as _________
CO, CO2, NO, NO2, SO2 and SO3.
Generally molecules that are gases at room temperature have fewer than ____ atoms from the first or second period.
5
What are the characteristics of gases?
- Gas particles are (close or far apart?).
- A gas has no definite ______ or ______ and will _________ fill any container.
- The attractive forces between gas particles are _________
Gas particles are far apart.
A gas has no definite shape or volume and will completely fill any container.
The attractive forces between gas particles are minimal
What is the KINETIC MOLECULAR THEORY OF GASES?
It is a model for the behavior of a gas; helps us understand gas behavior.
The KINETIC MOLECULAR THEORY OF GASES:
- A gas consists of small particles (______ or ________) that move ________ with ______ velocities.
This causes a gas to fill the _______ ______ of a container.
atoms or molecules that move randomly with high velocities.
entire volume
The KINETIC MOLECULAR THEORY OF GASES:
- The attractive forces between the particles of a gas are usually very _________.
Gas particles are _______ ______ and fill a container of _________ size or shape.
small
far apart; fill a container of any size or shape
The KINETIC MOLECULAR THEORY OF GASES:
- The actual volume occupied by gas molecules is considered _______ ________ compared with the volume that the gas occupies.
The volume of the gas is considered ______ the volume of the container.
Most of the volume of a gas is _____ ______, which allows gases to be easily ________.
extremely small
equal to
empty space, compressed
The KINETIC MOLECULAR THEORY OF GASES:
- Gas particles are in constant motion, moving _______ in ________ paths.
When gas particles collide, they ______ and travel in _______ __________. Every time they hit the walls of the container, they ____ ____.
An increase in the number of collisions against the walls of the container causes an increase in the ___________.
rapidly, straight
rebound, new directions, exert pressure
pressure of the gas
The KINETIC MOLECULAR THEORY OF GASES:
The average kinetic energy of gas molecules is proportional to the _____ temperature.
Gas particles move ______ as the temperature increases. At higher temperatures, gas particles hit the walls of the container _______ often, with _______ force, producing _______ pressures.
Kelvin
faster
more, more, higher
When we talk about a gas, we describe it in terms of 4 properties, which are….
pressure, volume, temperature and the amount of gas
See the chart on page 217 for a summary of the four properties of a gas (Table 6.1)
What is atmospheric pressure?
The gas particles in the air, mostly oxygen and nitrogen, exert a pressure on us called ATMOSPHERIC PRESSURE.
As you go to higher altitudes, the atmospheric pressure is less because there are fewer particles in the air.
PRESSURE (P):
The most common units used for gas pressure measurement in the US are _______ and ________.
…or __________ in other countries.
- the atmosphere (atm)
- millimeters of mercury (mmHg)
… kilopascals
VOLUME (V):
The volume of gas equals ___________
When you inflate a tire or a basketball, you are ____________. The _______ in the number of particles hitting the walls of the object _______ its volume.
The most common units for volume measurements are _____ and ______
the size of the container in which the gas is placed.
…adding more gas particles; increase, increases
liters (L) and milliliters (mL)
TEMPERATURE (T):
The temperature of a gas is related to the _____ ______ of its particles.
Although you measure gas temperature using a ________ thermometer, all comparisons of gas behavior and all calculations related to temperature must use the ______ temperature scale.
kinetic energy
Ex: if we have a gas at 200 K in a rigid container and heat it to a temperature of
400 K, the gas particles will have twice the kinetic energy that they did at 200 K.This also means that the gas at 400 K exerts twice the pressure of the gas at 200 K.
Celsius; Kelvin
AMOUNT OF GAS (n):
Usually we measure the amount of gas by its mass in ___________. In gas law calculations, we need to change the ____ of gas to ________.
grams
grams; moles
When billions and billions of gas particles hit against the walls of a container, they exert __________, which is defined as _______________ (also give the formula)
pressure
a force acting on a certain area
Pressure (P)= force/area
The atmospheric pressure can be measured using a ____________.
One ATMOSPHERE (atm) is defined as EXACTLY __________ mmHg
One atmosphere is also ______ torr, a pressure until named to honor the inventor of the barometer.
barometer
760 millimeters of mercury
760 torr. Because they are equal, until of torr and mmHg are used interchangeably.
1 atm= 760 mmHg = 760 torr (exact)
1 mmHg = 1 torr (exact)
In SI units, pressure is measured in _______.
1 atm is equal to ____________ of these.
pascals (Pa)
1 atm= 101.325 Pa
Because pascal is a very small unit, it is likely that pressures would be reported in kilopascals.
1 atm= 1.01325 x 10^5 Pa = 101.325 kPa
The US equivalent of 1 atm is ___________.
14.7 lb/in.^2 (psi)
1 atm= 14.7 lb/in.^2
Atmospheric pressure changes with variations in ________ and ________.
weather and altitude
hot day- a column of air has more molecules, which increase the pressure on the mercury surface. The mercury column rises, indicating a higher atmospheric pressure.
rainy day- atmosphere exerts less pressure, which causes the mercury column to fall. (Low pressure system)
above sea level- the density of the gases in the air decreases, which causes lower atmospheric pressures.
below sea level- at the Dead Sea, the atmospheric pressure is greater than 760 mmHg. Divers must be concerned about increasing pressures on their ears and lungs.
BOYLE’S LAW- Pressure and Volume
When a change in one property causes a change in another property, the properties are related. If the changes occur in opposite directions, the properties have an INVERSE RELATIONSHIP.
The inverse relationship between PRESSURE and VOLUME of a gas is known as BOYLE’S LAW.
The law states that the volume (V) of a sample of gas changes inversely with the pressure (P) of the gas as long as there is no change in the temperature (T) or amount of gas (n).
P1V1= P2V2
In BOYLE’S LAW, if the volume or pressure of a gas sample changes without any change in the temperature or in the amount of the gas, the new pressure and volume will give ______.
…the same PV product as the initial pressure and volume. Then we can set the initial and final PV products equal to each other.
CHARLES’S LAW: Volume and Temperature
The volume (V) of a gas is directly related to the temperature (T) when there is no change in the pressure (P) or amount (n) of gas.
A direct relationship is one in which the related properties increase or decrease together.
For 2 conditions, we can write Charles’s law as follows:
V1/T1 = V2/T2
All temperatures used in gas law calculations must be converted to their corresponding ______ temperatures.
Kelvin (K)
To determine the effect of changing temperature on the volume of a gas, the pressure and the amount of gas are kept constant. If we increase the temperature of a gas sample, we know from the kinetic molecular theory that the motion (kinetic energy) of the gas particles will ________.
To keep the pressure constant, the volume of the container must _______.
If the temperature of the gas decreases, the volume of the container must _______ to maintain the same pressure when the amount of gas is constant.
increase
increase
decrease
GAY-LUSSAC’s LAW:
Temperature and Pressure
The pressure of a gas is directly related to its Kelvin temperature.
An increase in temperature increases the pressure of a gas and a decrease in temperature decreases the pressure of the gas, as long as the volume and amount of gas do not change.
P1/T1 = P2/T2
What is VAPOR PRESSURE?
Each liquid exerts its own vapor pressure at a given ______________.
Liquid molecules with sufficient kinetic energy can break away from the surface of the liquid as they become gas particles or vapor.
In an open container, all the liquid will eventually evaporate.
in a closed container, the vapor accumulates and creates pressure called VAPOR PRESSURE.
Each liquid exerts its own vapor pressure at a GIVEN TEMPERATURE.
A liquid reaches its boiling point when its vapor pressure _________________.
…becomes equal to the external pressure.
As boiling occurs, bubbles of the gas form within the liquid and quickly rise to the surface.
EX: at an atmospheric pressure of 760 mmHg, water will boil at 110 degreesC, the temperature at which its vapor pressure reaches 760 mmHg
At higher altitudes, atmospheric pressures are _______ and the boiling point of water is _____ than 100 degrees C.
lower, lower
The boiling point differs, depending on the atmospheric pressure of a particular location.
A boiling temperature below 100 degrees C means that it takes longer to cook food. Some people will use a pressure cooker to obtain high temperatures (water is heated in a closed container so that pressures above 1 atm are obtained, which raises the boiling temperature of water above 100 degrees C).
Hospitals use an autoclave to sterilize lab and surgical equipment.
What is the COMBINED GAS LAW?
All of the pressure-solums-temperature relationships for gases that we have studied may be combined into a single relationship called the COMBINED GAS LAW.
This is useful for studying the effect of changes in TWO of these variables on the third as long as the amount of gas (number of moles) remains constant.
P1V1/T1 = P2V2/T2
What is AVOGADRO’S LAW?
The volume of a gas is directly related to the number of moles of a gas when temperature and pressure do not change.
Ex: if the number of moles of a gas is doubled, then the volume will also double as long as we do not change the pressure or the temperature.
V1/n1 = V2/n2
Using Avogadro’s law, we can say that any two gases will have _______ volumes if they contain the same number of moles of gas at the same __________ and ________.
equal, temperature and pressure
What are STANDARD TEMPERATURE and STANDARD PRESSURE?
To help us make comparisons between different gases, arbitrary conditions called STANDARD TEMPERATURE (273 K) and STANDARD PRESSURE (1 atm) together abbreviated STP, were selected by scientists.
Standard temperature is exactly 0 degrees C (273 K)
Standard pressure is exactly 1 atm (760 mmHg)
What is MOLAR VOLUME?
At STP, one mole of any gas occupies a volume of 22.4 L, which is about the same as the volume of 3 basketballs.
This volume, 22.4 L, of any gas at STP is called its MOLAR VOLUME.
When a gas is at STP conditions (_____ degrees C and _____ atm), its molar volumed can be used to write conversion factors between the number of moles of gas and its volume, in liters.
The molar volume conversation factors are used to convert between the number of moles of gas and its ________.
0 degrees C and 1 atm
MOLAR VOLUME CONVERSION FACTORS:
1 mole of gas at STP= 22.4 L of gas
1 mole gas (STP)/22.4 L gas and
22.4 L gas/ 1 mole gas (STP)
The molar volume conversation factors are used to convert between the number of moles of gas and its VOLUME.
What is DALTON’s LAW? (Partial Pressure)
Many gas samples are a mixture of gases. In gas mixtures, scientists observed that all gas particles behave in the same way. Therefore, the total pressure of the gases in a mixture is a result of the collisions of the gas particles regardless of what type of gas they are.
In a gas mixture, each gas exerts its PARTIAL PRESSURE, which is the pressure it would exert if it were the only gas in the container.
DALTON’s LAW states that the total pressure of a gas mixture is the sum of the partial pressures of the gases in the mixture.
Ptotal = P1 + P2 + P3 + …
The ______ of gas molecules, not the _____, determines the pressure in a container.
The NUMBER of gas molecules, not the TYPE OF GAS, determines the pressure in a container.
The air you breathe is a mixture of gases. What we call the atmospheric pressure is actually the sum of _______________.
the partial pressures of the gases in the air.
