What is the number of moles of vapor remaining in the flask? please help need it to study for final?

A student collected the following data using the procedure described in this experiment.
Atmospheric pressure = 752.6 torr
Temperature of the water bath at the time of removal = 99.6°C
Mass of empty flask = 135.263 g
Mass of flask containing condensed sample = 135.684 g
Volume of water used to fill up the flask = 263.9 mL

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