Gas laws Flashcards
describe the motion of the particles in solids
particles cannot move, they can only vibrate in fixed positions
describe the motion of the particles in liquids
particles have more energy and can break away and slide over eachother
describe the motion of the particles in Gas
particles have the most energy and are widely spaced moving at great speed
What is diffusion?
Diffusion is the movement of a substance from an area of high conc to an area of low conc
What are the factors involved when describing gases?
Temperature
Pressure - the force a gas exerts on a unit area
Volume
how do you turn degrees into kelvin
+273
how do you turn pascals into kilopascals
divide by 1000
what is boyle’s law
boyles law states that for a definite mass if gas at a constant temperature, pressure is inversely proportional to volume
( P1V1 = P2V2)
What is charles law
Charles law states that for a definitye mass of a gas at constant pressure, volume is directly proportional to temperture (ONLY WHEN IN KELVIN)
V1/T1 = V2/T2
What is the combined gas law?
P1V1/T1 = P2V2/T2
conditions 1 = conditions 2
What is Gay- Lussac’s law of combining volumes?
In a reaction between gases there is a simple whole number ratio of volumes of reactants and products at the same conditions of temper ture and pressure
What is avogardo’s law?
it states that equal volumes of gasses at the same conditions of temperture and pressure have equal numbers of molecules ( and therefore equal number of moles)
Volume of any gas at standard tempweature and pressure (s.t.p)
22.4L
volume of any gas at room temperture and pressure
24 L
Outline the assumptios if the kinetic theory of gases
- Gasses are made up of particles inn continous, rapid, random, straight line motion, colliding with eachother and within the walls of their container
- there are no attractive or replusive forces betweem the olecules of a gas
- The volume of the molecules is negligible compared to the space they occupy
- collisions between moleules are perfectly elastic - no loss of kinetic energy
- The average kinetic energy of molecules is directly proportional to the temperature in kelvin
What is an ideal gas
an ideal gas is one that perfectly obeys all the gas laws under all conditions of temperture and pressure
Outline why real gases deviate from ideal gas behaviour/What are limitations of the kinetic
theory of gases?
real gasses;
have attractive forces between their molecules- intermolecular forces
the volume of molecules is not always negligible compared to the space they occupy
at what conditions do real gasses come closest to ideal gas behaviour
at low pressures - molecules are widely spaced
at high tempertures - molecule have enough energy to overcome attractive or replusive forces
Which of the noble gases would you expect to behave most like an ideal gas?
Justify your answer
helium
ideal gasses have no attractibe or replusive forces between the molecules
helium in the noble gas with the smallest mass and therefore has the weakest ( van der waal) forves
what is the Ideal gas equation?
pV=nRT
pressure (Pa)
Volume (m3)
number of moles of gas
universal gas constant =8.3
temperture (K)
Describe the procedure of measuring the relative molecular mass of a volatile
liquid (using a conical flask)
use electronic balance, get mass of clean conical flaks,rubber band and alumium foil.
add small volume of propanone/cytohexane place in beaker full of water, prick foil with hole, fasten with rubber band.
heat water with hotplace close to boiling point, vaporising the propanone.
allow conical flask to cool to room temp, vapour wiil condence.
dry outside and find mass
subtract intial mass from final,
this gives the mass of the volatile liquid that has vaporised and condensed again.
calculate the relative molecular mass of a volatile liquid
To measure the relative molecular mass of a volatile
liquid (using a conical flask)
What is meant by a volatile liquid? Name a volatile liquid suitable for this experiment
a liquid with a low boiling point
propanone/cyclohexane
how is the temperture of the vapor obtaied
using a thermometer to measure the temperature of the water- the temperature of the vapour can be assumed to be equal to the temperature of the water
how is the pressure of the vapour in the conical flask measured?
a barometer is used to measure stomspheric pressure. The pressure of the vapour in the concial flask will be the same as atomspheric pressure due to the pin hole made in the foil
how is the volume of the volatile liquid found?
The volume of the vapour is found by filling the conical flask that will be filled with the vapour completely with water, pouring it in a graduated cylinder and reading its volume
Why is this method unsuitable for non-volatile liquids?
the boiling points of non-voatile liquids are too high, boiling water will not vapourise them.
What modern instrumental technique can be used as a more accurate method to measure the relative molecular mass of volatile and non-volatile liquids as well as of solid and gaseous
substances?
Mass spectrometry
Give three errors in this expeirment that may lead to innaccurate results
the entire conical flask should be overed in boiling water to ensure the temperture of the vapour is the same temperature of the water- which is diffucult to achieve
the outside of the conical flask and aluminium foil may not be completely dry when finding out their mass for the second time
the electronic balance may only read to an accutacy of one or two decimal places
