the first on about hess law
In this experiment, you will measure the amount of heat released in these three related reactions:
Reaction 1. NaOH (s) Na+
(aq) + OH-
(aq) H1
Reaction 2. NaOH (s) + H+
(aq) + Cl-
(aq) H2O + Na+
(aq) + Cl-
(aq) H2
Reaction 3. Na+
(aq) + OH-
(aq) + H+
(aq) + Cl-
(aq) H2O + Na+
(aq) + Cl-
(aq) H3
and the second on is
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) + 2 HCl(aq) ↔ H2O(l) + MgCl2(aq)
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