What is Heat of Solution and Why Should You Care?
Heat of solution, also known as molar enthalpy, is the total heat absorbed (or released) when a solute dissolves in a solvent. This concept has practical applications in everyday life and various scientific fields, from cooking to chemical engineering.
When you dissolve something like salt or sugar in water, an energy change occurs. This change can either be endothermic (absorbing heat) or exothermic (releasing heat). Knowing the heat of solution helps you predict these changes.
How to Calculate Heat of Solution
Step 1: Determine the Total Energy Absorbed
Use the formula:
[Q = c \times m \times \Delta T]
Where:
- Q is the total energy absorbed (in Joules)
- c is the specific heat capacity (in J/gยฐC)
- m is the mass of the solution (in grams)
- ฮT is the change in temperature (in ยฐC)
Step 2: Determine the Number of Moles of Solute
Calculate the number of moles of solute you have dissolved.
Step 3: Calculate the Heat of Solution
[\text{HS} = \frac{Q}{n}]
Where:
- HS is the heat of solution (molar enthalpy)
- Q is the total energy absorbed
- n is the total number of moles of solute
Calculation Example
Given 500 grams of water, a temperature change from 25ยฐC to 30ยฐC, and the specific heat capacity of water is 4.18 J/gยฐC:
[Q = 4.18 \times 500 \times (30 - 25) = 4.18 \times 500 \times 5 = 10450 \text{ J}]
If we dissolved 2 moles of solute:
[\text{HS} = \frac{10450 \text{ J}}{2 \text{ moles}} = 5225 \text{ J/mol}]
The heat of solution is 5225 J/mol.