What relates qrxn and qsur?

The relationship between qrxn (heat of reaction) and qsur (heat of surrounding) is described by the first law of thermodynamics, which states that the heat released or absorbed by a reaction is equal and opposite to the heat gained or lost by the surrounding environment. In an exothermic reaction, qrxn is negative and qsur is positive as heat is released to the surroundings. In an endothermic reaction, qrxn is positive and qsur is negative as heat is absorbed from the surroundings.