Endothermic reactions

2 marks · Easy

A reaction absorbs 45 kJ of heat energy when exactly 1.5 mol of the substance react completely. Calculate the enthalpy change, ΔH, for this reaction in kJ/mol. State your answer with the correct sign.

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ΔH = +30 kJ/mol (±1)

Also accept: +30; 30 kJ/mol; +30 kJ/mol

Common mistakes: –30, wrong sign

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Marking points

M1 · 1 mark · Uses correct formula: ΔH = q / n; substitutes 45 kJ and 1.5 mol correctly.

A1 · 1 mark · Final answer given as +30 kJ/mol, with correct sign and units.

Worked solution

ΔH = q / n