The decomposition of hydrogen peroxide is given by this equation: 2h2o2(l) ? 2h2o(l) o2(
g. calculate the mass of water (in grams) and the volume of oxygen at stp formed when 2.00x10-3 mol of hydrogen peroxide is decomposed.

From the given balance equation, every 2 moles of H2O2 will decompose to 2 moles of H2O and 1 mole of O2.

H2O:     (2 x 10^-3 mol H2O2) x (2 moles H2O/ 2 moles H2O2) x (18 g H2O/mol)
                            = 0.036 grams H2O

O2:    (2 x 10^-3 mol H2O2) x (1 mol O2/ 2 moles H2O2) x (22.4 L O2/ 1 mol O2)
                             = 0.0224 L O2

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.