A student uses and Erlenmeyer flask with a total volume of 127.8 ml . The mass o

ID: 780896 • Letter: A

Question

A student uses and Erlenmeyer flask with a total volume of 127.8 ml .

The mass of the flask assembly was 119.419 g before the volatile liquid was added.

It was 119.702 g after vaporization.

The molecular mass of the liquid is 50.49 g/mol.

The pressure was recorded as 763.4 torr and the water bath was 283.44 K.

a. What mass of gas remained in the flask after vaporization?

b. How many moles of gas were in the flask?

c. What is the molar volume of the liquid?

d. What was the student's reported value for "R"?

WORK MUST BE SHOWN...

A).. m g= 119.702g - 119.419g = 0.283g

B).. 0.283g x (1mol / 50.49g) = 0.005605 mol
C).. molar volume = volume per mole

= 127.8mL / 0.005605g x 1L / 1000mL

= 22.8L

D)

.
. PV = nRT
rearranging.
.. R = (V/n) x P/T
solving..
.. R = (22.8L) x (763.4torr x 1atm / 760torr) / (283.44K)

= 0.0808 Latm/molK

the accepted value is 0.08206 Latm/molK

percent error = |0.0808 - 0.08206| / |0.08206| x 100% = 1.54%

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