Cobalt iii hydroxide and nitric acid react according to the following balanced equation:
co(oh)3 (aq) + 3 hno3 (aq) --> co(no3)3(aq) + 3 h2o(l)
a. what mass of cobalt iii hydroxide is needed to make 5.2 liters of a 0.42 m cobalt iii hydroxide solution?
b. how many milliliters of 1.6 m nitric acid is needed to completely react with the amount of cobalt iii hydroxide in part 2a above?
c. based on parts 2a and 2b above, how many moles of water would be produced?

The mass of cobalt (III) needed is
m = 5.2 L (0.42 mol/L) ( 93 g/mol)
m = 97.65 g

The volume of nitric acid needed is
V = 5.2 L (0.42 mol/L) (3 mol / 1 mol) (1000 mL/1.6 mol)
V = 1968.75 mL

The moles of water produced is
n = 5.2 L (0.42 mol/L) (3 mol / 1 mol)
n = 3.15 moles

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.