The isotopic effect in hydrogen results in which of the following observable differences between and — Hydrogen Chemistry Question

💡 Solution & Explanation

$D_2$ has a higher bond dissociation enthalpy than $H_2$ ($443.3 \text{ kJ mol}^{-1}$ vs $436.0 \text{ kJ mol}^{-1}$), causing $D_2$ to react slower (the isotopic effect). $D_2$ actually has a *higher* melting and boiling point than $H_2$.