Question

A sample of a volatile liquid is vaporized completely in a 240.0 cm3 flask at 99°C and 757 mm Hg. The condensed vapor weighs 0.465 g.
What is the molar mass of the liquid?

Answer 1

PV=nRt
or
n=PV/RT
n= no. of moles

now convert the units to match R's unit
R the ideal Law gas constant = 8.31 J/KT

so remember J=m^3*Pa

Pressure=(in Pa) 133.2*757mmHg =
Volume =(in m^3) = 240*10^-6 m^3=
R=8.31 J/KT
T (in K) = 99C+273 =

place this in our formula and we will have our moles = ?moles

molar mass = 0.465g./?moles

Answer 2

so it's the same as the mass of the condensed vapor?

Answer 3

Yes. Mass is conserved.

Answer 4

oh thanks you

Answer 5

You're welcome.

Answer 6

oh wait i was only able to do conversion at operation as of now. and i got 0.0078. hmmmm why??

Answer 7

Did you be careful to use consistent units with your R value?

Answer 8

yes i actually tried it twice. same outcome though

Answer 9

I converted to Liters, Kelvin, and atm and used 0.0820574 for R. I got n=0.00783 moles. Then mass/moles gives molar mass.

Answer 10

ohhh exactly the same haha. mass of what should be used? in mass/moles :)

Answer 11

:) the mass given in the problem statement.

Answer 12

oh right my bad haha :)
so 59.62 g/mol

Answer 13

Yes, that is what I get. :)

Answer 14

wahha thankyou :)))

Answer 15

Good job. :)

Answer 16

No worries.