posted by Sara on .
two hydrates were weighed, heated to drive off waters of hydration, and then cooled. The residues were then rewieghed. Based on the follwing results, what are the formulas of the gydrates?
Compound. Initial mass. M after cooling
NiSO4*xH2O 2.08 1.22
CoCl*xH2O 1.62 .88
#1. mass water evolved = 2.08-1.22 = 0.86 grams.
mass anhydrous NiSO4 = 1.22 grams
moles H2O = 0.86/18 =0.0478
moles NiSO4 = 1.22/154.76 = 0.00788.
Divide by the smaller to find the ratio to 1 mole NiSO4.
0.00788/0.00788 = 1 NiSO4
0.0478/0.00788 = 6.06
round these to 1 NiSO4 to 6 H2O and the formula is
Check my work.
The Co one is done the same way. Check to make sure that Co formula isn't CoCl2.xH2O.
Sorry that might be a little unlclear..I hope this helps
Initial mass: 2.08
Mass after cooling: 1.22
Initial mass: 1.62
Mass after cooling: .88
I understand now...THANK YOU!