Part T:Hyarates Hydrates are crystalline compounds in which one or more molecule

Question

Part T:Hyarates Hydrates are crystalline compounds in which one or more molecules of water are combined with each formula unit of a salt. The water is not bound tightly and can usually be driven off by subjecting the crystals to the hottest flame of a Bunsen burner for 5 to 10 minutes. If the hydrate is colored, a color change usually results upon heating as the anhydrous salt forms. For example the following change occurs upon heating: CuSO4·5H2O (s) bright blue CuSO4 (s)+5 HO (g) white A generalized form of this reaction is: CuS 04.xH2O(s) CuSO4 (s) + x H2O(g) Recall that the percentage of a component in a compound is calculated by: (Part/whole) x 100=% Preliminary Questions (5 p Describe how you could find the % by mass of water in the hydrate CuSO4·5H20 assuming that yo did not already know the formula. Be specific and list the laboratory procedural steps you would t in the order that you would perform them.

Explanation / Answer

Solution :-

#1) Preliminary question Calculating the percent (%) of water in the hydrate (CuSO4.5H2O)

Weigh known amount of the CuSO4.5H2O and place in then Gouche crucible then heat it on the Bunsen burner for the 5-10 minutes until the constant mass is obtained by evaporating the water from the hydrate.

Then calculate the mass of water lost by heating.

Mass of water lost = [original mass of CuSO4.5H2O] - [mass of anhydrous salt (CuSO4) after heating ]

Then using the mass of water lost and origonal mass of the hydrate sample we can calculate the percent of water in the hydrate using the following formula

% water = [mass of water / mass of hydrate sample] *100 %

#2) Calculating the moles of water

Formula to calculate the moles is as follows

Moles = mass of water in gram / molar mass water

So using the mass of water lost we can divide it with molar mass of water to get the moles of water.

#3) Calculating the moles of CuSO4

To calculate the moles of CuSO4 we need to use the mass of CuSO4 salt remain after heating and divide it with molar mass of CuSO4

Moles of CuSO4 = mass of CuSO4 / molar mass of CuSO4

#4) Calculating the relative number of moles of salt and water

Using the following formula we can find the relative number of moles of salt and water

Relative number of moles of salt and water (x) = moles of water / moles of CuSO4 salt

#5)To find the coefficient to place in front of the H2O in the hydrate formula

The relative number of moles of salt to water is nothing but the coefficient of the H2O which is used in the hydrate formula

CuSO4.XH2O

So use the value of the X calculated in the (#4)

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