Chapter 9 - Gases

Question 1

Gases

Answer 1

particles have greater internal kinetic energy (relative to each other) compared to any other state of matter
gases expand to fill their container
not visible to the eye
can be mixed more effectively, which is important for chemical reactions
difficult to control in open containers, density differences can be used to sort them
gases are 1000 times more empty space, so the reaction rate may be reduced

Question 2

Measuring amounts of gas

Answer 2

mass cannot be measured due to buoyancy
volume on its own depends on the size of the container
temperature (measure of the average kinetic energy of the particles of a substance) can be measured
three types of kinetic energy = translational, rotational, vibrational
pressure can be measured as it is force per area

Question 3

Pressure

Answer 3

pressure of a gas depends on force and area
force = collisions between molecules and sides of container
force is affected by: number of molecules, volume of container, speed of molecules (temperature), frequency of collisions
area = surface area of walls of the container

Question 4

Ideal gases

Answer 4

particles move in straight lines until they collide with other particles
volume of the particles is practically zero compared to total volume of gas
the IMF are practically zero compared to the effect of kinetic energy so that the collisions are elastic and the particles don’t stick to each other
these criteria are met when the temperature is much higher than the boiling point, and when they are spherical particles
water is not an ideal gas

Question 5

Atmospheric pressure

Answer 5

force of molecule collisions divided by surface area of container
pressure decreases as the altitude increases because there is less weight of air above you
current air pressure given is the pressure the environment would be at if it was at sea level
therefore, altitude must be accounted for to determine exact pressure

Question 6

Calculating pressure

Answer 6

when the water level in a test tube is higher than the water level of the container it is in, the pressure inside the tube is lower than the pressure outside
this is because gravity is pulling down on the liquid in the test tube, increasing the volume of the gas inside
therefore, when the water level is the same, pressure outside equals pressure of the gas inside

Question 7

Gas Laws

Answer 7

Boyle’s Law
Pressure-Temperature Law
Combined Gas Law
Charles Law
Dalton’s Law

Question 8

Molar volume at SATP

Answer 8

T = 25 C
P = 100 kPa
n = 1
V = 25