Energy is either absorbed or released for all chemical reactions, and we call this energy the enthalpy of reaction (?Hrxn). If the enthalpy of reaction is positive, then we say that the energy was absorbed or that the reaction was endothermic. If the enthalpy of reaction is negative, then we say that energy was released or that the reaction was exothermic. Most chemical reactions are exothermic. In this problem, you will measure the amount of heat released when solid MgO is reacted with aqueous HCl to form water and then you will calculate the heat of reaction.

MgO(s) + 2HCl(aq) = H2O(l) + MgCl2(aq)

A weigh paper will be on the balance with approximately 2.81 g MgO on the paper. The calorimeter will be on the lab bench and filled with 100 mL 1.000 M HCl.

Data Table: Mass MgO: 2.8045g initial temperature(°C): 24.99°C final temperature(°C): 25.00 °C

Calculate the number of moles of MgO used in the reaction. The molar mass of MgO is 56.305 g/mole.