A student is given a green solid that is a sample of a hydrated nickel (II) sulf
ID: 821386 • Letter: A
Question
A student is given a green solid that is a sample of a hydrated nickel (II) sulfate. the student weighs the sample in a dry covered crucible and obtains a mass of 22.326g for the crucible, cover, and hydrate sample. Earlier they had found that the crucible and cover weighed 21.244g. The student heats the crucible to drive off the water vapor, keeping the crucible red hot for about 10 minutes witht eh cover slightly ajar. the students lets the crucible cool and finds that the crucible, cover, and contents weigh 21.840g after heating. During heating, the sample turned from green into a yellow solid.
a)How many moles of H20 are presnt pre mole of NISO4???? show work please
b) what is the complete chemical formula and name of the hydrate????
c)what is the % water in the hydrate???? show work please
Explanation / Answer
Mass of hydrated salt = mass of sample before heating
= total mass before heating - mass of crucible and cover
= 22.326 - 21.244 = 1.082 g
Mass of NiSO4 = mass of sample after heating
= total mass after heating - mass of crucible and cover
= 21.840 - 21.244 = 0.596 g
Mass of H2O = mass of hydrated salt - mass of anhydrous salt
= 1.082 - 0.596 = 0.486 g
(a) Moles of NiSO4 = mass/molar mass of NiSO4
= 0.596/154.76 = 0.003851 mol
Moles of H2O = mass/molar mass of H2O
= 0.486/18.02 = 0.02697 mol
Moles of H2O/moles of NiSO4 = 0.02697/0.003851 = 7
=> there are 7 moles of H2O per mole of NiSO4
(b) Chemical formula of hydrate: NiSO4.7H2O
Name of hydrate: Nickel(II) sulfate heptahydrate
(c) Percent water in hydrate = mass of water/mass of hydrate x 100%
= 0.486/1.082 x 100%
= 44.9%
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