how many gas molecules does the flask contain?

Question

An open flask sitting in a lab fridge looks empty, but we know that actually it is filled with a mixture of gases called air. If the flask volume is 0.00415 m3 and the air is at standard temperature and pressure, how many gas molecules does the flask contain?

One mole of ideal gas at STP occupies 0.0224 m3. One mole of any compound contains 6.022 × 1023 molecules (Avogadro\'s number).

Answer 1

We know that 2.24 × 10^-2 m³ of air at STP contains 6.022 × 10²³ molecules.

The flask has a volume of 4.15 × 10^-3 m³ and the air in it is at STP.

Since we have the number of molecules to volume at STP, we can set equal the ratios

(molecules in flask) / (4.15 × 10^-3 m³) =( 6.022 × 10²³ molecules) / (2.24 × 10^-2 m³)

molecules in flask = ( 6.022 × 10²³ molecules) × (4.15 × 10^-3 m³)/(2.24 × 10^-2 m³)

molecules in flask = ( 6.022 × 10²³ molecules) × 0.185

molecules in flask = 1.114 × 10²³ molecules