See section on enthalpy for a more detailed explanation. ... The standard enthalpy of reaction is symbolized by ΔHº or ΔHº_rxn and can take on both positive and negative values. The units for ΔHº are kiloJoules per mole, or kj/mol.

Can the enthalpy be negative?

A negative enthalpy represents an exothermic reaction, releasing heat. A reaction that absorbs heat is endothermic. Its enthalpy will be positive, and it will cool down its surroundings. This reaction is exothermic (negative enthalpy, release of heat).

Can you have a negative molar enthalpy?

Molar heat of solution, or, molar enthalpy of solution, is the energy released or absorbed per mole of solute being dissolved in solvent. If heat is released when the solute dissolves, temperature of solution increases, reaction is exothermic, and ΔH is negative.