Look at the diagram below. According to the diagram, what substance(s) are the reactant(s)?

NH3(aq) and HCl(aq) are the reactants, while NH4Cl(aq) is the product.

Explanation:

The hydrogen atom from the HCl molecule joins the other three in NH3 creating a four hydrogen molecule,  NH4Cl.

-20kJ/mol minus 66kj/mo

Explanation:

2NO2 = N2O4

Delta H 2NO2 = +66 kj/mol

Delta H N2O4 = -20kJ/mol

Change in entropy = Change in heat of a system

Delta H = Hfinal minus Hinital

So in our case it would be

-20kJ/mol minus 66kj/mol