Question

Explain in detail the experimental procedure you would use to find heat of solution when sodium chloride is dissolved into water. (Answer in detail.)

Answer 1

A solute dissolves in excess solvent to form a solution:

solute + solvent solution

Heat of solution (or enthalpy of solution) is the energy released or absorbed when the solute dissolves in the solvent. And molar heat of solution (or molar enthalpy of solution) is the energy released or absorbed per mole of solute being dissolved in solvent.

Heat of solution can be determined in the laboratory by measuring the temperature change of the solvent when solute is added.

To calculate the enthalpy (heat) of solution using experimental data:

Step 1:

Amount of energy released or absorbed is calculated

q = m x C x T

q = amount of energy released or absorbed
m = mass
C = specific heat capacity
T = change in temperature

Step 2:

calculate moles of solute

n = m / M

n = moles of solute
m = mass of solute
M = molar mass of solute

Step 3:

Amount of energy (heat) released or absorbed per mole of solute is calculated

H_soln = q / n

H_soln = molar enthalpy (heat) of solution
q = amount of energy (heat) released or absorbed
n = moles of solute ΔH is negative if energy (heat) is released (exothermic).