Waiting for answer This question has not been answered yet. You can hire a professional tutor to get the answer.

# Should I take into account the water of a hydrate when calculating the molar mass in order to find the limiting reactant of the equation ? 2 CuSO4(dot)5H20 + 2 Na2CO3 ---> CuCO3Cu(OH)2 + 2 Na2SO4 + CO2 +4 H20

Yes, you need to take the water of hydration into account.

As you know, hydrates are salts that have **water of hydration** associated with their crystal structure.

This means that you need to take into account the added water molecules when trying to figure out how many moles of ##"CuSO"""_4## you have in solution.

You can think about hydrates as being impure samples. In this case, each mole of copper(II) sulfate, ##"CuSO"""_4##, comes attached to five moles of water.

Let's say that your reaction requires the presene of **0.5 moles** of ##"CuSO""_4##. For anhydrous copper(II) sulfate, this is equivalent to a mass of

##0.5color(red)(cancel(color(black)("moles"))) * "159.6 g"/(1color(red)(cancel(color(black)("mole")))) = "79.8 g"##

The molar mass of the pentahydrate is ##"249.685 g/mol"##. If you use **78.9 g** of pentahydrate, you only get

##78.9color(red)(cancel(color(black)("g"))) * ("1 mole CuSO"""_4 * 5"H"_2"O")/(249.7color(red)(cancel(color(black)("g")))) = "0.320 moles CuSO"""_4 * 5"H"_2"O"##

Since each mole of pentahydrate contains one mole of copper(II) sulfate, adding this much pentahydrate will be equivalent to adding **3.20 moles** of ##"CuSO"""_4##.

In this example, to get **79.8 g** of ##"CuSO"""_4##, you need to use the of the hydrate.

##(159.6color(red)(cancel(color(black)("g/mole"))))/(249.7color(red)(cancel(color(black)("g/mole")))) * 100 = 63.9%##

This means that you get **63.9 g** of ##"CuSO"""_4## for every **100 g** of ##"CuSO"""_4 * 5"H"_2"O"##. This means that you have

##79.8color(red)(cancel(color(black)("g CuSO"""_4))) * ("100 CuSO"""_4 * 5"H"_2"O")/(63.9color(red)(cancel(color(black)("g CuSO"""_4)))) = "124.9 g CuSO"""_4 * 5"H"_2"O"##

So yes, you need to take into account the water of hydration when doing stoichiometric calculations.

If a problem tells you that **100 g** of copper(II) sulfate pentahydrate are dissolved in solution and made to react with a certain mass of sodium carbonate, you need to take into account the water of hydration when you calculate the number of moles of ##"CuSO"""_4##.

.