Avagadros law states that the volume of a gas is directly proportional to the number of moles at constant temperature and pressure conditions [tex] \frac{V}{n} [/tex] = k where V - volume n - number of moles and k - constant [tex] \frac{V1}{n1} = \frac{V2}{n2} [/tex] parameters for the first instance are on the left side and parameters for the second instance are on the right side of the equation V1 - 4.50 L V2 - 1/2 x 4.50 = 2.25 L n1 - 2.00 mol substituting the values in the equation [tex] \frac{4.50L}{2.00 mol} = \frac{2.25 L}{n} [/tex] n = 1.00 mol 1.00 mol of the gas is present when container is 1/2 in size