How many moles does 8.19 L of gas at STP represent?

Explanation:

           According to Avogadro's Law, same volume of any gas at standard temperature and pressure will occupy same volume. And one mole of any Ideal gas occupies 22.4 dm³ (1 dm³ = 1 L).

Data Given:

                 n = moles = ?

                 V = Volume = 16.8 L

Solution:

               As 22.4 L volume is occupied by one mole of gas then the 16.8 L of this gas will contain

                          = ( 1 mole × 16.8 L) ÷ 22.4 L

                          = 0.75 moles

Result:

          16.8 L of Nitrogen gas will contain 0.75 moles at standard temperature and pressure.

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.