Gaw Laws from Grade 10 Science

1. GAS LAWSWAYLIE NINA D. DE CLARO | SCIENCE 10 | TAAL NHS

4. A bicycle tire was inflated to a pressure of 3.74
atm during early morning when the
temperature was 15ºC. At noontime, the
temperature rose to 35ºC. What was the
resulting pressure in the tire (assuming that its
volume did not change)?
SELF TEST:

5. A 5000 mL container is filled with helium gas to a
pressure of 3.0 atm at 250ºC. Approximately how many
toy balloons at STP can be filled by helium from this
container, assuming each balloon can contain 1 L?
Recall that STP means standard temperature and
pressure (1 atm and 273 K).
ASSIGNMENT:

6. Lorenzo Romano Amedeo Carlo Avogadro
 Count of Quaregna and Cerreto
 made important contributions in shedding light on
reaction stoichiometry.
 provided explanations as to why compounds reacted in
definite ratios and on how the amount of gas affects its
volume. Experimentally, the most convenient way of
quantifying the amount of gas is through its mass.
 played an important role in providing evidence of the
existence of atoms. Eventually the number of molecules in
a mole is named after him.

7. Lorenzo Romano Amedeo Carlo Avogadro
 In 1811, he wrote in a paper that, “Equal volumes of all
gases, kept at the same pressure and temperature,
contain the same number of molecules.”
 He was the first to suggest that the volume of a gas is
directly proportional to the number of moles of gas
present at a given temperature and pressure.

8. Using the proportionality symbol, we can express the
proportionality between the volume and the number of mole of a
gas as:
 V α n at constant T and P
 Mathematically, the Avogadro’s Hypothesis can be expressed as:
 where V is the volume of gas n is the amount of gas in moles
and k is a proportionality constant
 This can also be expressed as:

9. Let’s have more problem sets!
 A 7.25 L sample of nitrogen gas is determined to contain 0.75 mole of
nitrogen. How many moles of nitrogen gas would there be in a 20L
sample provided the temperature and pressure remains the same?

10. Can we observe Avogadro’s hypothesis in
real life scenarios?
Try to observe the baking of bread or cake at the
nearest bakery in your place. How can you explain the
phenomenon of having a bigger bread or cake
compared with the dough?
Can you also use this law to explain the production of
balloons and the way vulcanizing shop deals with flat
tires?

11. Boyle’s Law Problem
 A sample of Ne gas occupies 0.220L at 0.86 atm.
What will be its volume at 29.4kPa?
 t 1.70 atm, a sample of gas takes up 4.25L. If the
pressure in the gas is increased to 2.40 atm, what
will the new volume be?

12. Charle’s Law Problem
 A balloon takes up 625L at 0°C. If it is heated to 80°C,
what will its new volume be?
 A gas at 40.0°C occupies a volume of 2.32L. If the
temperature is raised to 75.0°C, what will the new
volume be if the pressure is constant?

13. Gay-Lussac's Law
 If the pressure in a car tire is 1.88 atm at 25°C, what will be the
pressure if the temperature warms to 37°C?
 The pressure in a sealed can of gas is 235kPA when it sits at room
temperature (20°). If the can is warmed to 48°C, what will the new
pressure inside the can be?
 A car tire has a pressure of 2.38 atm at 15.2°C. If the pressure
inside reached 4.08 atm, the tire will explode. How hot would the
tire have to get for this to happen? Report the temperature in
degrees Celsius.

14. Combined Gas Law
 A gas at 110kPa at 30.0°C fills a flexible container with an initial
volume of 2.00L. If the temperature is raised to 80,0°C and the
pressure increases to 440Kpa, what is the new volume?
 A 40.0L balloon is filled with air at sea level (1.00 atm, 25.0°C). It is
tied to a riavk and thrown in a cold body of water, and it sinks to
the point where the temperature is 4.0°C and the pressure is 11.0
atm. What will its new volume be?

16. Ideal Gas Law
A gas that behaves exactly as described by the gas
laws is called an ideal gas.
Many gases, especially at high pressure or low
temperatures do not behave quite ideally, hence
they are called real gases.

17. Ideal Gas Law
If we combine the relationships expressing Boyle’s
Law,
V α 1 / P,
Charles’ Law,
V α T

18. Ideal Gas Law
and the proportionality
V α n
where (n stands for the number of moles of gas),
we obtain the relationship:
V α nT / P.

19. Ideal Gas Law
By introducing a constant, this relationship can be
expressed as the equation V = RnT/P, and further
simplified to
PV = nRT
 where R is called the universal gas constant

20. Checkpoint
What is the volume of 1 mole of an ideal gas at
STP?
 Recall:
 A chemist named Amadeo Avogadro studied the properties of
many different gases. In 1811, he concluded that equal volumes of
all gases, when measured under the same conditions of
temperature and pressure, always contain the same number of
molecules.

21. Checkpoint
This relationship, V α n, is known as the Avogadro’s
Law, which you encountered at the beginning of
the lesson. It is very useful because it tells us that
one mole of an ideal gas (it doesn’t matter which
type of gas!) at STP will always occupy 22.4 L.

22. Checkpoint
Is the following statement true or false?
“The density of a gas varies with temperature and
pressure.”

23. Ideal Gas Law
 What is the pressure in atm of a 0.108 mol sample of the gas at a
temperature of 20.0°C if its volume is 0.505L?
 2.3 moles of Helium gas are at a pressure of 1.70 atm, and the
temperature is 41°C. What is the volume of the gas?
 At a certain temperature, 3.24 moles of CO2 gas at 2.15 atm take
up a colume of 35.28L. What is this temperature (in Celsius)?

24. Assignment 4.8
 Complete the following table:
Data on a sample of oxygen gas.
 What is the Kinetic Molecular Theory?
n ? T V ?
0.00625 mol 1.0 atm 293 oK ? 0.08206

25. Gas Practice Questions
 1.) Convert 539 torr to atm.
 2.) A gas takes up 25.2 liters at 25oC. At 25oC, the gas can also take
up 12.2 liters at 1500 torr. What was the pressure, in atm, of the
original sample?
 3.) A gas takes up 14.8 liters of 24oC. What temperature in kelvin is
required to obtain a volume of 25.0 liters at constant pressure?
 4.)How many moles of chlorine gas are present at 25oC, 762 torr, with
a volume of 14.2 L?

26. Gas Practice Questions
 5.) If "Bor" (thats the name of a person) has a sample of gas that has
a volume of 8.2 liter at 25oC and 2 atm, how much volume will it take
up if you decrease pressure to 1.5 atms and icrease temperature to
100oC?
 6.) 25 liters of gas A is pumped into a container at 25oC and 760 torr
with 20 liters of gas B at 25oC and 700 torr. Calculate the total
pressure when both gases are pumped into a tank with 10 liters at
25oC.
 7.) Calculate the mole fraction of oxygen when 200 torr of air (760
torr total) is oxygen.

27. Gas Practice Questions
 1.) Just set up a simple ratio.
539 torr * (1 atm/760 torr) = 0.709 atm
 2.) Use this formula:
P1V1 = P2V2
460 atm * 1.20 liters = 839 torr * V2
V2= 0.658 L

28. Gas Practice Questions
 3.) You will use the ratio P1V1 = P2V2 in order to solve this equation.P1V1 = P2V2
25.2 liters * P1 = 12.2 liters * (1500 torr / 760 torr)
Note that you have to convert the torr to atm. The problem asks for the final pressure in atms. You could
of just solved the ratio without the conversion, and converted the answer later. Either way is acceptable.
25.2 liters * P1 = 24
P1 = 0.956 atm
 4.) Use the formula:V1/T1 = V2/T2
14.8 liters / 297 torr = 25.0 liters / x
14.8 x = 7425
x = 502 K

29. Gas Practice Questions
 5.)PV = nRT (the ideal gas law! Note: you will see this a LOT in gases,
so memorize it)
n = PV/RT
P = (762 torr/760 torr) = 1.00atm
n = (1.00 atm * 14.2 L) / (298oK * 0.08206)
n = 0.582 moles

30. Gas Practice Questions
 6.) PV = nRT
 n = PV/RT
 = (2 atm * 8.2 L) / (0.08206 * 298oK) = 0.671 moles
 Now, you must remember that you are taking this amount and changing it some more. So, you
do this again, this time, solving for VOLUME. (No, the initial 8.2 doesn't count, because you are
manipulating the environment)
 PV = nRT
 V = nRT/P
 =(0.671 moles * 0.08206 * 373oK) / 1.5 atm = 13.76 liters