To determine for 2 H₂O(g)→2 H₂(g)+O₂(g)

CHEMISTRY · Subjective · A Level · Chemistry · Energetics · Energetics

Problem

To determine

\Delta H

for 2 H₂O(g)→2 H₂(g)+O₂(g), a student used the reference data (I) H₂(g)+

\frac{1}{2}

O₂(g)→H₂O(l)

\Delta H

-285.8\,\text{kJ}

(II) H₂O(l)→H₂O(g)

\Delta H

+44.0\,\text{kJ}

. The student wrote 1. H₂O(l)→H₂(g)+

\frac{1}{2}

O₂(g)

\Delta H

-285.8\,\text{kJ}

2. H₂O(l)→H₂O(g)

\Delta H

+44.0\,\text{kJ}

and reported

\Delta H

-241.8\,\text{kJ}

for the target reaction. Identify the two procedural errors in the student’s work and state the corrected value of

\Delta H

(in kJ) for 2 H₂O(g)→2 H₂(g)+O₂(g).