# chem - pressure

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A closed vessel with volume of 226.9mL initially contained air at 680.8mmHg at 16.5 degrees celcius.
A sample of an organic liquid of mass 0.113g was injected into the flask which was then warmed to 124.9 degrees celcus causing all the organic liquid to vaporise. The final pressure inside the container was then 1268.7mmHg. (give answers to 1 decimal point):
a) air pressure inside at 124.9 degrees celcius? _____mmHg

b) pressure due to organic vapour at 124.9 degrees celcius? ____mmHg
c) Molar mass of organic compound? ____g mol^-1

• chem - pressure - ,

Note the correct spelling of celsius.
a. Use P1/T1 = P2/T2 to calculate the pressure due to the air at the new temperature.

b. Total pressure @ 124.9 - pressure air @ 124.9 = pressure organic liquid @ 124.9

c. Use PV = nRT. Use P of organic liquid in atmospheres, don't forget to change T to Kelvin, and calculate n = number of moles.
Then moles = grams/molar mass.
Post your work if you get stuck.

• chem - pressure - ,

i did p1/t1 =p2/t2 converted celsius to kelvin
i get 935.5 mmHg for a

then 333.2 for b

i don't get c