Q in chemistry from Bmat 2017

[Raph]

Hello!

Hydrated copper(II) sulfate has the formula CuSO4*5H2O.
100 cm3 of a solution contained 10g of hydrated copper(II) sulfate. What is the concentration, in mol/dm3, of this solution?
(A, values: H=1.0; O=16; S=32; Cu=64)
A 0.100 mol/dm3
23
B
0.400 mol/dm3
C 0.495 mol/dm3
D
0.532 mol/dm3
E
0.562 mol/dm3
F
0.625 mol/dm3
Bmat 2017

So, what does " hydrated copper(II) sulfate" mean? why is the formula CuSO4*5H2O presented like that and how should I regard the 5 molecules of water in it? is it part of the compound? guidelines or a worked out solution will be very much appreciated

[Juliette]

hi
yes this is a good trap, you need to count the 5H2O in the compound’s molecular weight
the copper sulfate has bound to 5 water molecules to form a crystalline solid
for example, bath salts have the structure MgSO4 * 7H2O but they are not wet but hard dry crystals even though most of it’s mass is water!
Mw = 250
C = n/V = 10/250 / 1/10 = 0,4 mol/dm³
is this the correct answer?

[Raph]

Juliette you did it again! thank you