Anal0387: percent water in a hydrate
3. the mass of a crucible and a hydrated salt was found to be 21.447 g. the mass of the crucible and the
anhydrous salt was 20.070 g. the mass of the crucible was 17.985 g.
(1) calculate the mass of the hydrate heated.

Mass of the hydrate heated = 3.462 g

Mass of the hydrate = mass of crucible and hydrate salt– mass of the crucible  

Mass of crucible and hydrates salt = 21.447 g  

Mass of the crucible = 17.985 g  

Therefore;

Mass of the hydrate = 21.447 g – 17.985 g  

                                    = 3.462 g  

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)