4.3 Gases

Question 1

What is the property of gases related to shape and volume

Answer 1

no definite shape or volume - gas fills to occupy its container

Question 2

What is the property of gases related to compression

Answer 2

compressible - gases can be compressed in a container, a ballon can be squeezed smaller

Question 3

What is the property of gases related to diffusion

Answer 3

quick diffusion - gases will rapidly diffuse within a contained space

Question 4

What is the property of gases related to density

Answer 4

have low density - usually around 1/1000 the density of the solid

Question 5

What is the property of gases related to exerting pressure

Answer 5

Exert pressure - The gas in a balloon pushes back when the balloon is squeezed.

Question 6

What are gases related to kinetic energy

Answer 6

gases have the most kinetic energy of the three main matter states and their molecules move around the most and are generally free to disperse

Question 7

What is the Kinetic Molecular Theory of gases (K.M.T)

Answer 7

The Kinetic Molecular theory of gases is a theory that describes the behaviour of a theoretical ideal gas (no gas exists that fully fits)

Question 8

What is the first statement of K.M.T

Answer 8

Ideal gases consist of small particles (atoms or molecules) that are far apart in relation to their own size.

Question 9

What is the 2nd statement of K.M.T

Answer 9

The gas particles move in a rapid, random, straight-line motion.

Question 10

What is the 3rd statement of K.M.T

Answer 10

The collisions of particles with each other or the walls of the container are perfectly elastic; no loss of energy occurs.

Question 11

What is the 4th statement of K.M.T

Answer 11

There are no attractive forces between particles or between particles and the walls of the container.

Question 12

What is the 5th statement of K.M.T

Answer 12

At any particular instant, all the particles in a given sample of gas do not contain the same kinetic energy. The average kinetic energy of the sample is proportional to the temperature.

Question 13

If we raise the temp of a gas in a container what happens to pressure

Answer 13

If we raise the temperature of a gas the speed of molecules increases, this then exerts a higher pressure on the container as the particles hit the sides with greater force and also hit the sides with more frequency

Question 14

What is the Effect of the number of molecules on pressure

Answer 14

Effect of the number of molecules on pressure– Injecting more gas molecules into a fixed volume will increase the number of collisions per second with the walls of the container and the pressure will increase.

Question 15

What is the Effect of the number of molecules on volume

Answer 15

Effect of the number of molecules on volume– The container will expand if it is able to. This might happen in a balloon when more air is blown into it.

Question 16

What is the Effect of the number of molecules on temperature

Answer 16

Effect of the number of molecules on temperature– Increasing the number of molecules does not directly affect the temperature. However, if the pressure and volume do not rise, then clearly the temperature must have been lowered. If the temperature did not change, either the pressure or the volume, or both, would have to increase. The only way to prevent this is to lower the temperature.

Question 17

What is molar volume

Answer 17

In chemistry we measure the volume occupied by a mole of a gas at a specific temp and pressure as molar volume

Question 18

What are the standard temp and pressure for molar volume

Answer 18

Standard temperature is0oC. Standard pressure is101.3 kPa. 0oC was chosen because it is the melting point of water and is easily reproduced. All that is needed is an ice/water bath. 101.3 kPa is the normal air pressure at sea level.

Question 19

what is molar volume at STP

Answer 19

One mole ofany gasoccupies22.4 L (28cm3) at STP (standard Temperature and Pressure)

Question 20

what is SATP

Answer 20

SATP is stands for Standard Ambient Temperature and Pressure which is defined as 25oC and 100 kPa.

Question 21

what is molar volume at SATP

Answer 21

The volume of one mol of gas at SATP (Standard Ambient Temperature and Pressure) is24.8 L/mol.

Question 22

What is an important note for STP

Answer 22

In 1982, the International Union of Applied and Pure Chemists (IUPAC) changed the official definition of Standard Temperature and Pressure. This resulted in the new molar volume at STP being 22.7 L/mol.
The old value of 22.4 L/mol is still widely used however. Examples, questions and solutions in this course use the 22.4 L/mol value.