Question

0. A liquid solution of LiCl in water at 25°C contains 1 mol of LiCl and 7 mol of water. If 1 mol of LiCl⋅3H2O(s) is dissolved isothermally in this solution, what is the heat effect?

Answer 1

Answer:

19.488 kJ

Explanation:

The overall reaction mechanism shows the reaction between LiCl and H₂O

$LiCl.3H_2O ------> Li +\frac{1}{2} Cl_2+3H_2+\frac{3}{2} O_2$     -------- (1)

$2Li+Cl_2+10H_2O ----->LiCl.10H_2O$              -------- (2)

$3H_2+\frac{3}{2}O_2 -----> 3H_2O$                                     --------- (3)

$LiCl.7H_2O ------> Li + \frac{1}{2} Cl_2+7H_20$             ---------- (4)

The overall reaction =

$LiCl.7H_2O +LiCl.3H_2O ------> 2LiCl.10H_2O$

The heat effects of the above reactions from 1-4 respectively are in the order ; 11311.34 kJ, -857.49 kJ, -873.61 kJ and 439.288kJ respectively

The overall enthalpy change is:

$\delta H = \delta H _{LiCl.3H_2O}+\delta H_{3H_2O} + \delta H_{2(LiCl.5H_2O)} + \delta H _{liCl.7H_2O}$

$\delta H =Q$ at constant pressure;

Thus; Q = 1311.3 (kJ)  857.49 (kJ) -873.61 (kJ) + 439.288 (kJ)

Q = 19.488 kJ

Thus, the heat effect = 19.488 kJ after the addition of  1 mol of LiCl⋅3H2O(s)