Question

Given the following equation and heat of reaction: 2 moles of A combine with 2 moles of B to produce 6 moles of C and 26 kJ What will be the change in enthalpy in kJ of the reaction of 1 mole of A combining with 1 mole of B to produce 3 moles of C? Include the sign but no units.

Answer 1

Answer: The change in enthalpy will be -13.

Explanation:-

Endothermic reactions are those in which heat is absorbed by the system and exothermic reactions are those in which heat is released by the system.

$\Delta H$ for Endothermic reaction is positive and  $\Delta H$ for Exothermic reaction is negative.

$2A+2B\rightarrow 6C+26kJ$  

$2A+2B\rightarrow 6C$       $\DeltaH=-26kJ$

When 1 mole of A combining with 1 mole of B to produce 3 moles of C

Thus as the stoichiometry has got half of the original , enthalpy of the reaction will also get half.

Thus for reaction :

$A+B\rightarrow 3C+\frac{26}{2}kJ$  

$A+B\rightarrow 3C$       $\DeltaH=-13kJ$

Thus the change in enthalpy will be -13.