Question

What is the percentage of water in the hydrate CoCl2 • 6H2O? 

Can someone help me with this one?

Answer 1

You need the periodic table. Get the molar mass for each one. C is 12, O is 16, 2Cl is 71 (35.45 x 2), H2O is 18 x 6 of them is 108. Add them up and you get 207 g/mol. What is the percentage of water? Since you have 6 water molecules, and it is equal to 108, you simply divide 108 and 207. You get a decimal. Multiply it by 100%. You'll get 52.17%.

Answer 2

Answer: 45.4%

Step-by-step 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%