Gases

Question 1

Does Random motion occur in Gases?

Answer 1

Yes. The molecules are not constrained

Question 2

How is kinetic energy proportional to temperature?

Answer 2

An increase in temperature will also increase kinetic energy and vice versa. this means collisions will also be increased/ decreased

Question 3

What is the relationship between gasses, pressure and volume?

Answer 3

The volume of a given gas is inversely proportional to the pressure (provided constant temp)

P1V1=P2V2

Question 4

How does inhalation and exhalation occur when humans breathe?

Answer 4

Inhalation = occurs when the ribcage expands and the diaphram moves downward, increasing the volume and decreasing the pressure

Exhalation = the rib cage contracts and the diaphram moves up, decreasing volume and increasing pressure

• the expansion of the chest cavity reduces pressure in the intrapulmonary and intrapleural cavity, hence causing the lungs and alveoli to expand with pressure

Question 5

How is lung collapse prevented?

Answer 5

The difference in pressure between the intrapleural and intrapulmonary cavities stop lung collapse

Question 6

When does Boyle’s law apply?

Answer 6

Only for gases that are not too dense and not close to boiling point

Question 7

What is the relationship between gas volume and temperature?

Answer 7

V1/V2=T1/T2

Question 8

What is Charle’s Law?

Answer 8

The volume of a fixed quantity of gas at constant pressure is proportional to temperature

Question 9

When do gases liquify? and what is absolute 0?

Answer 9

at low temperatures, absolute 0 = 273.15 degrees

Question 10

How to calculate the temperature in Kelvins?

Answer 10

Temperature in Celcius + 273.15

Question 11

What is Guy Lussac’s law?

Answer 11

When volume is constant, the pressure is directly proportional to temperature
when T is in Kelvins = P1V1/T1 = P2V2/T2

Question 12

What variables are needed to define the state of gases?

Answer 12

temp
pressure
volume
number of mols of gas

Question 13

What is the Ideal Gas Law?

Answer 13

PV=nRT

the volume of an enclosed gas increases in direct proportion to the mass of gas present

Question 14

What is Standard temperature and pressure (STP)?

Answer 14

t=273.15K
P= 101.3kPA
volume = 22.4L per mol

Question 15

What does Avogadro’s number say?

Answer 15

Equal numbers of gases at the same pressure/ temperature must have the same number of molecules

Question 16

How can partial pressure help to identify the ideal gas law?

Answer 16

PV = nRT

(P1+P2+P3 etc) XV = (n1+n2+n3 etc) XRT

Question 17

How does concentration effect flow rate?

Answer 17

The greater the difference in concentration per unit distance, the greater the flow rate

Question 18

How does water equalise partial pressure?

Answer 18

Water flows one way until the pressure of water is the same on both sides (equil), and there is no net flow of water

Question 19

How can the osmotic pressure due to solute molecules be given?

Answer 19

pi=(n/v) X RT

Question 20

How does partial Pressure effect the number of molecules striking the surface?

Answer 20

They are proportional to one another

• eg: If we compress the gas to a smaller volume, the same number of molecules are now acting against a smaller surface area, so the number striking per unit of area, and thus the pressure, is now greater

Question 21

What is dynamic equilibrium?

Answer 21

Between gas and liquid phases, as many molecules of gas that enter the solution also leave it

Question 22

What is Henry’s law?

Answer 22

The equilibrium concentration of dissolved gas is proportional to the partial pressure of that gas above the liquid

Question 23

Describe how Nitrogen Narcosis is caused?

Answer 23

• When diving deep underwater breathing high pressure air, N2 dissolves in the blood in very large concentrations
• If the diver rises quickly, pressure of air is reduced, and the partial pressure of nitrogen drops and causes bubbles of N2 to form in the bloodstream which can cause death

Question 24

What is the rate of vapouration dependent on?

Answer 24

temperature

Question 25

What is saturated vapour pressure?

Answer 25

the equilibrium pressure of a gas phase above a liquid of the same molecules

Question 26

How can water’s SVP change?

Answer 26

at body temp (37) SVP= 6kPA
at 100 degrees SVP= 101kPA
at boiling point of any liquid SVP= atmospheric pressure

Question 27

Can the ideal gas law be applied to SVP?

Answer 27

No. You must use the known SVP values for water vapour and apply the ideal gas law to any remaining gases