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Question

When 27.98 g of hydrated tin (II) chloride was heated up, 18.97 g of the anhydrous salt was left. how do you Determine the formula of the hydrated salt.

Answer 1

When heated, water is lost from the hydrated compound.  Thus, find the mass lost, and that will be equal to the mass of water that was in the compound.

 

27.98 g - 18.97 g = 9.01 g = mass of H₂O in original sample

SnCl₂ molar mass = 189.7 g/mole

mass of  anhydrous SnCl₂ = 18.97 g

moles anhydrous SnCl₂ 18.97 g x 1 mole/189.7 g = 0.1 moles

moles H₂O in original sample = 9.01 g x 1 mole/18 g = 0.5 moles H₂O

Multiplying both by 10 to get whole numbers gives the formula SnCl₂·5H₂O as the formula of the hydrated salt.

Tin(II) chloride pentahydrate