What happened to the number of moles in a sample that originally occupied 500ml with 2.50 moles and then occupied 750ml?
it deals with gas laws

The number of moles that initially occupied a 250ml container remains the same when it occupied 750ml container but they are freer because the 750ml container is bigger and has more space. So the gases now occupied more space and their movement is less curtailed unlike when they were in 250ml container

1 is the answer to this problem

answer : (a) volume of the gas = 8.67 ×   l

                (b) second virial coefficient b = -1.21226 l/mole

solution :   given,     t = 300k

                                p = 20atm

                                z = 0.86

                                n = 8.2 mmoles = 8.2 × moles

                                r =   0.082 l atm/k/mol

        find,     (a) volume of gas   and (b) second virial coefficient b at 300k.

formula used :            

                          and            

(a)            

                    = \times 0.082\times 300}{20}[/tex]

                    = 8.67 ×   l

(b)      

                    = (0.00867-1) × 8.659

                    = - 8.5839 l/mole