The breakdown of a certain pollutant X in sunlight is known to follow first-order kinetics. An atmospheric scientist studying the process fills a 20.0-L reaction flask with a sample of urban air and finds that the partial pressure of in the flask decreases from 0.473 atm to 0.376 atm over 5.6 hours.
Calculate the initial rate of decomposition of X, that is, the rate at which X was disappearing at the start of the experiment. Round your answer to significant digits. Round your answer to 2 significant digits.

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. 

The correct answer is weight.

Qand k are only the same when the forward rate of the reaction has reached zero.