LC CHEMISTRY- EXPERIMENT: TO MEASURE THE RELATIVE MOLECULAR MASS OF A VOLATILE LIQUIDLC CHEMISTRY- EXPERIMENT: TO MEASURE THE RELATIVE MOLECULAR MASS OF A VOLATILE LIQUID

REBECCA'S LC CHEMISTRY- TO MEASURE THE RELATIVE MOLECULAR MASS OF A VOLATILE LIQUID KNOWT

Volatile liquid

liquid with low boiling point

Relative molecular mass

average mass of a molecule compared to 1/12 of the carbon 12 isotope

label this diagram

• pinhole

• aluminium foil

• boiling water

• vapour

• hotplate

• rubber band

• thermometer

How is mass of volatile liquid measured (using words, 3 points needed)

• get mass of flask and foil

• heat until liquid is gone

• get mass of sample by subtraction

How is volume of container measured (using words, 2 points needed)

• fill flask with water

• empty into graduated cylinder

How temperature at which temperature took place

use thermometer to measure temperature of water

How could the pressure be measured

barometer

describe this diagram using words with diagram

• flask covered with foil with pinhole

• immersed so that at least half is underwater

how is the volatile liquid vapourised

hotplate under beaker

why pressure of vapour at the end of heating stage of the experiment was known to be equal to the atmospheric pressure

vapour escaped due to pinhole

describe the mass of the vapour in the container at the end of the heating stage was found

subtract mass of flask initially from mass of flask at end

account for volatility of bromine boing point 58.8c compared to that of water 100 c

hydrogen bonds in water

example of volatile liquid suitable for this experiment

acetone (propanone)

why is the method unsuitable for liquids that are non-volatile/unstable

high boiling point

What modern instrumental technique could be used as a more accurate method to measure the relative molecular masses of volatile and non-volatile liquids as well as of solid and gaseous substances?

mass spectrometer