Appropriate units to express heat of solution are $$J \cdot mol^{-1}$$ or $$kJ \cdot mol^{-1}$$
. The heat of solution, also known as enthalpy of solution, signifies the amount of energy that is released or absorbed when a solute dissolves in a solvent
. To calculate molar enthalpy of solution:
- Determine the amount of energy that is released or absorbed (q) using the formula $$q = m \times C_g \times \Delta T$$, where:
- $$q$$ = amount of energy released or absorbed
- $$m$$ = mass
- $$C_g$$ = specific heat capacity
- $$\Delta T$$ = change in temperature
- Calculate the number of moles of solute (n) with the formula $$n = m \div M$$, where:
- $$n$$ = moles of solute
- $$m$$ = mass of solute
- $$M$$ = molar mass of solute
- Calculate the amount of energy (heat) released or absorbed per mole of solute ($$\Delta H_{soln}$$) using the formula $$\Delta H_{soln} = q \div n$$, where:
- $$\Delta H_{soln}$$ = molar enthalpy (heat) of solution
- $$q$$ = amount of energy (heat) released or absorbed
- $$n$$ = moles of solute
When including the sign for $$\Delta H_{soln}$$, remember that if heat is released, the reaction is exothermic and $$\Delta H$$ is negative. If heat is absorbed, the reaction is endothermic and $$\Delta H$$ is positive
