Spontaneity and the sign of ΔG

(i) Calculate, in $\mathrm{kJ\,mol^{-1}}$, the standard enthalpy change of this hydrogenation reaction using the enthalpy of combustion data in section 14 of the data booklet. (ii) The standard entropy change for this reaction is…

A reaction is spontaneous at low temperatures but becomes non-spontaneous when the temperature is raised. Which combination of signs of $\Delta H$ and $\Delta S$ is consistent with this behaviour? A. $\Delta H > 0$ and $\Delta S > 0$ B. $\Delta H < 0$ and…

(i) Using section 12 of the data booklet, determine the standard enthalpy change of the reaction, in $\mathrm{kJ\,mol^{-1}}$. (ii) A value obtained from bond enthalpies is less accurate than one obtained from enthalpies of formation. State two reasons why.…

When the cell discharges, a spontaneous redox reaction generates a potential difference between the electrodes and the temperature of the cell rises. (i) Deduce the signs of $\Delta H_\mathrm{discharge}$, $E_\mathrm{cell}$ and $\Delta G_\mathrm{discharge}$.…

Pentadecane can be cracked into smaller molecules. Consider the reaction: $\ce{C15H32(g) -> 3C4H8(g) + C3H8(g)}$ where $\ce{C4H8}$ is but-1-ene. (i) Use the bond enthalpies in section 12 of the data booklet to determine $\Delta H^\ominus$ for this reaction.…