Estimate the change in enthalpy, Delta H, for the following reaction:
H2(g) + Cl2(g) --> 2 HCl(g)
To work this problem, think of the reaction in terms of simple steps:
1. First, the reactant molecules, H2 and Cl2, break down into their atoms
H2(g) --> 2 H(g)
Cl2(g) --> 2 Cl(g)
2. Next, these atoms combine to form HCl molecules
2 H(g) + 2 ...