Consider the following reaction: Cl2 + Na2S → 2NaCl + S
The percent yield of sulfur when 71.0 g of Cl2 is
reacted in excess Na2S solution is 73.0 %.
What is the actual mass of sulfur yielded by this
reaction?
(Molar mass of S = 32.1 g/mol, molar mass of Cl2 = 71.0
g/mol)

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.