Serum taken from a patient being treated with lithium for
manic-depressive illness was analyzed for lithium concentration. a
reading of 212 units was obtained for the intensity of the 671 nm
red emission line. then 1.00 ml of a 11.2 mm lithium standard was
added to 9.00 ml of serum, and this spiked serum gave an intensity
reading of 546 units. what is the original concentration of li in
the serum?

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. 

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Idon't know hope someone you