Question

A hydrated sample of cobalt II chloride has a molar mass of 309.99 g/mol. What is the mole ratio between cobalt II chloride and water?

Answer 1

Step-by-step explanation:

Let there be 1 mole of CoCl2.

Mass of CoCl2 = 1mol * (129.839g/mol) = 129.839g

Mass of H2O = 309.99g - 129.839g = 180.151g

Moles of H2O = 180.151g / (18g/mol) = 10mol

Hence the mole ratio of CoCl2 to H2O is 1 : 10.

Answer 2

`\boxed {\boxed {\sf 1 \ mole \ CoCl_2 \ to \ 10 \ mole \ H_2O}}`

Step-by-step explanation:

First, identify the formula of cobalt II chloride: CoCl₂

Next, find the molar mass of CoCl₂. Identify the individual element's mass.

• Cobalt (Co): 58.93319 g/mol
• Chlorine (Cl): 35.45 g/mol

Since there is a subscript of 2 after the Cl, we must multiply the molar mass of chlorine by 2

• CoCl₂: (58.93319 g/mol) + (2* 35.45 g/mol) = (58.93319 g/mol)+(70.9 g/mol)
• 129.83319 g/mol

Assuming the sample is 1 mole, we can subtract the mass we just found from the hydrate sample's mass. This is the mass of the water.

• 309.99 g - 129.83319 g= 180.15681 g

Now, we need to find the number of moles of water. Begin by finding the molar mass of water: H₂O

• Hydrogen (H): 1.008 g/mol
• Oxygen (O): 15.999 g/mol

Since there is a subscript of 2 after the H, we must multiply the molar mass of hydrogen by 2.

• H₂O: (1.008 g/mol *2)+ 15.999 g/mol = (2.016 g/mol)+(15.999 g/mol)=18.006 g/mol

Finally, divide the mass of the water by the molar mass of water.

• 180.15681 g / 18.006 g/mol

Note that the grams or g will cancel.

• 180.15681 / 18.006 mol = 10.00537654 mol

This is roughly 10, so we can round to 10.

• ≈ 10 mol H₂O

So, the mole ratio is 1 mole CoCl₂ to 10 mole H₂O