PROBLEM 60P

How much energy is released when 2.55 kg of diethyl ether freezes?

Solution 60P

Step 1:

Amount of diethyl ether((C2H5)2O)= 2.55 Kg

Energy released when 2.55 kg of diethyl ether freezes = ?

Heat must be removed from the (C2H5)2O to cause it to freeze.

The amount of heat released by freezing 1 mole of water is 7.27 kJ/mol.

Formula to calculate the heat required :

q = mHf

where, q = heat in kJ,

m = mass(in grams),

Hf = heat of fusion

We have Hf in terms of moles, but the mass is given in Kg. So let’s convert the mass in Kg to g and then find the number of moles for the given amount of (C2H5)2O.

First, let’s convert mass in Kg to g :

1 kg = 1000g.

Therefore, 2.55 Kg in g will be :

= 2.55 kg

= 2550 g.

Now, let’s find number of moles :

Number of moles(m) =

Molar mass of (C2H5)2O = 74.12 g/mol

Therefore, number of moles =

= 34.40 moles.

So, number of moles in 2550 g of (C2H5)2O is 34.40 moles.