Nitrogen from a mixture of nitrogen and oxgen

Oxygen - nitrogen gas mixture is a colorless odorless gas. Both oxygen and nitrogen are noncombustible; however, oxygen can accelerate the burning of a fire. Under prolonged exposure to fire or intense heat the containers may rupture violently and rocket.

Explanation:

The liquid nitrogen and oxygen are then separated by fractional distillation . The liquefied air is passed into the bottom of a fractionating column. Just as in the columns used to separate oil fractions , the column is warmer at the bottom than it is at the top.

when the volume of gas is   changed from   717.73 ml   to 852 ml   the temperature will   change   from 315   c to 452   c

    calculation

this is calculated using the charles law formula

that is,   v1/t1 = v2/t2

          v1=?

        t1 = 315 c   into   kelvin = 315 +273 = 588 k

        v2 = 852   ml

        t2 = 425c + 273 =698 k

make v1   the subject of the formula ( by   multiplying both side by t1)

  v1=( v2 xt1) / t2

v1= (852 ml   x 588 k)/ 698 k= 717.73 ml

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.