When a 21.5-g sample of LiCl was added to 195 g of water at a temperature of 20.00°C in a calorimeter, the temperature increased to 39.26°C. How much heat is involved in the dissolution of the LiCl?

Explanation:

In this case, to calculate the heat of solution (KJ/mol) we have to take into account the mass of water, the specific heat of the water and the temperature change, so:

Δ

With this in mind, we can use the equation:

If we plug the values into the equation we will have:

Now, with the mass value (21.5 g) and the molar mass of LiCl (42.39g/mol) we can calculate the moles of LiCl:

Now, in the heat of solution, we have KJ/mol units. Therefore, we have to convert from J to KJ:

Finally, we can divide by the moles of LiCl:

So, for each mole of LiCl, we have 63.09 KJ involved in the dissolution process.

I hope it helps!