Enthalpy Change - the overall energy exchange with the surroundings and when a change happens at constant pressure and the final temperature is the same and the starting temperature.
Exothermic - gives out energy (in the form of heat) to the surroundings. The heat leaves the system like people exit a building. The enthalpy change is negative as the system has lost heat.
Endothermic - takes in energy from the surroundings. The enthalpy change is positive as the system has gained energy.
Standard enthalpy of a reaction - is the energy transferred when the molar quantities or reactants as stated react under standard conditions (i atmospheric pressure, 298k, substances in their most stable conditions, solutions with concentration of 1…