1.A hydrated form of copper sulfate (CuSO4·x H2O) is heated to drive off all the

Question

1.A hydrated form of copper sulfate (CuSO4·x H2O) is heated to drive off all the water. If we start with 9.19 g of hydrated salt and have 5.87 g of anhydrous CuSO4 after heating, find the number of water molecules associated with each CuSO4 formula unit.

2.Iron(II) Sulfate forms a blue-green hydrate with the formula FeSO4 ·n H2O(s). If this hydrate is heated to a high enough temperature, H2O(g) can be driven off, leaving the dirty yellow anhydrous salt FeSO4(s). A 18.300-g sample of the hydrate was heated to 300 °C. The resulting FeSO4(s) had a mass of 9.9993 g. Calculate the value of n in FeSO4 ·n H2O(s).

3.The combustion of ethane (C2H6) produces carbon dioxide and steam:

2C2H6 (G)+7O2(G)------->4CO2 (G)+6H2O (G)

How many moles of CO2 are produced when 5.15 mol of ethane are burned in an excess of oxygen?

--------MOLS?

Explanation / Answer

Ans 1 :

Mass of water = 9.19 - 5.87 = 3.32 g

Mass of CuSO4 = 5.87 / 159.609 = 0.0368 moles

Number of moles of water = 3.32 / 18.01528 = 0.184 moles

Dividing the number of moles by a common value , we get the ratio as 1 : 5

So the formula of the compound will be : CuSO4.5H2O

So 5 molecules of water associated with each CuSO4 molecule

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