Washing soda, a compound used to prepare hard water for washing laundry, is a hydrate, which means that a certain number of water molecules are included in the solid structure. Its formula can be written as Na2CO3⋅xH2O, where x is the number of moles of H2O per mole of Na2CO3. When a 3.070 −g sample of washing soda is heated at 25 ∘C, all the water of hydration is lost, leaving 1.14 g of Na2CO3.

What is the value of x?

10

Explanation:

The detailed solution is contained in the image attached. The molar mass of hydrated and anhydrous salts are obtained and the number of moles of hydrated and hydrated salts are equated. The masses of hydrated and anhydrous salts are gives in the question and are simply substituted accordingly. This can now be used to obtain the number of molecules of water of crystallization as required in the question.

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