Question

When 0.250 moles of LiCl are added to 200.0 g of water in a constant pressure calorimeter a temperature change of +11.08°C is observed. Given that the specific heat of the resulting solution is 4.184 J g-1 °C-1 and we can ignore the small amount of energy absorbed by the calorimeter, what is the molar enthalpy of solution (ΔHsol) for LiCl?

Answer 1

Answer:

3.91 × 10⁴ J/mol

Explanation:

We can calculate the heat of solution using the following expression.

Q = c × m × ΔT

where,

c is the specific heat capacity of the solution

m is the mass of the solution

ΔT is the change in the temperature

The mass of LiCl is:

$0.250mol.\frac{42.39g}{mol} =10.6g$

The mass of the solution is:

m = mLiCl + mH₂O = 10.6 g + 200.0 g = 210.6 g

Q = c × m × ΔT = (4.184 J g⁻¹ °C⁻¹) × 210.6 g × 11.08 °C = 9763 J

In a constant pressure calorimeter, the molar enthalpy of solution for LiCl is:

$\Delta H_{sol}=\frac{9763J}{0.250mol} =3.91 \times 10^{4} J/mol$