The mass fractions of a mixture of gases are 15 percent nitrogen, 5 percent helium, 60 percent methane; and 20 percent ethane. This mixture is expanded from 200 psia and 4008F to 15 psia in an adiabatic, steady-flow turbine of 85 percent isentropic efficiency. Calculate the second law efficiency and the exergy destruction during this expansion process. Take T0 5 778F.

Ibelieve y y even though i've only taken chemistry for one year

Mass is the amount of matter in an object.  weight is the measurement of the pull of gravity on an object.  say for example, you travel to the moon which has a different gravitational field compared to the gravitational field of earth. (gravitational fields: earth = 1, moon = 0.165)  now when you are on the moon, the pull of gravity on you is different than on the earth. and as weight is the measurement of the pull of gravity on an object, that means yes, your weight can and will change on the moon.  however, on the moon, on earth or even on jupiter, the amount of mass inside of you remains the same. meaning your physical mass remains constant.  in conclusion it is possible for your weight to change as your mass remains constant. 

What do you not know about it