Partial Pressure Calculation for Argon Gas Collected Over Water at 30.0oC

[chem31sa6]

A sample of argon gas is collected over water at 30.0oC. The level of the
water is adjusted until the total pressure in the flask is 771 torr and the volume is 250.0
mL. The vapor pressure of water is 31.8 torr at 30.0oC.

A. How many moles of argon are in the flask?
B. What is the partial pressure of argon in the flask?
C. What is the total mass of gas in the flask?

I got:
a) 9.78e-3 mol
b) .973atm
c) 1.946 atm

 

[Borek]

And?

c is definitely wrong - mass is not measured in atm.