<p><math xmlns="http://www.w3.org/1998/Math/MathML"><mo>&#8710;</mo><mi>H</mi><mo>&#160;</mo><mo>&#60;</mo><mo>&#160;</mo><mo>&#8710;</mo><mi>U</mi></math>&nbsp;only if the number of moles of the products is greater than the number of moles of the reactants</p>