The decomposition of of NOCl(g) into NO(g) and Cl₂(g) has an enthalpy change of under…

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

Problem

The decomposition of

2\,\text{mol}

of NOCl(g) into NO(g) and Cl₂(g) has an enthalpy change of

+76\,\text{kJ}

under standard conditions. To supply heat while avoiding additional CO₂ emissions, only hydrogen combustion is allowed:

H_2(g) + \frac{1}{2}\,O_2(g) \to H_2O(l) \quad \Delta H = -286\,\text{kJ}\,\text{mol}^{-1}

. Plant specifications require the combined process to have an overall

\Delta H

between

-40\,\text{kJ}

and

-80\,\text{kJ}

per cycle and to use the smallest possible amount of H₂. Which hydrogen feed rate meets these criteria? (a)

0.40\,\text{mol}\,H_{2}

combusted per cycle (b)

0.30\,\text{mol}\,H_{2}

combusted per cycle (c)

0.45\,\text{mol}\,H_{2}

combusted per cycle (d)

0.50\,\text{mol}\,H_{2}

combusted per cycle