What is the percentage of water in the hydrate cocl2 • 6h2o?
can someone me with this one?

45.4%

Explanation:

1) The percentage of water must be calculated as a mass percent.

2) You need to find the mass of water, and the total mass in one formula unit. For that you need to use the atomic masses of each element along with the number of atoms of such element in the formula unit.

3) Atomic masses (taken from a periodic table).

Co: 58.933 g/mol

Cl: 35.453 g/mol

H: 1.008 g/mol

O: 15.999 g/mol

4) Mass of the formula unit:

CoCl₂ • 6H₂O

⇒ 58.933 g/mol + 2×35.453 g/mol + 6×2×1.008 g/mol + 6×15.999 g/mol =

= 237.929 g/mol

5) Mass of water in the formula unit:

6H₂O ⇒ 6×2×1.008 g/mol + 6×15.999 g/mol = 108.09 g/mol

6) Percent = [mass of water / mass of the formula unit]×100

= [108.09/237.929]×100 = 45.4%