Three single-step reactions have the following enthalpy changes ( ) and activation…

CHEMISTRY · Single correct · A Level · Chemistry · Energetics · Energetics

Problem

Three single-step reactions have the following enthalpy changes (

\Delta H

) and activation energies (

E_a

): • Reaction I:

\Delta H = -40\,\text{kJ mol}^{-1}

E_a = 50\,\text{kJ mol}^{-1}

• Reaction II:

\Delta H = -75\,\text{kJ mol}^{-1}

E_a = 70\,\text{kJ mol}^{-1}

• Reaction III:

\Delta H = -25\,\text{kJ mol}^{-1}

E_a = 35\,\text{kJ mol}^{-1}

Which ranking correctly orders the reactions from most exothermic to least exothermic? (a)

\text{II } > \text{III } > \text{I}

(b)

\text{III } > \text{I } > \text{II}

(c)

\text{II } > \text{I } > \text{III}

(d)

\text{I } > \text{II } > \text{III}