Energy in the Equation

ENERGY WHETHER ABSORBED OR RELEASED CAN BE ADDED TO THE EQUATION

Eg: 2C+3H2+0.5O2 ---> C2H5OH +235kJ

higher energy lower energy

* Exothermic reactions have energy term on the right hand side (RHS) and a negative delta H.

* Endothermic reactions have energy term on the left hand side (LHS) and a positive delta H.

ENERGY CALCULATIONS

Delta H = energy change in a reaction and expressed in kJ/ mole of one of the chemicals in the equation

EG: CH4+2O2 ---> Co2+2H2O +812kJ

Delta H of this exothermic reaction is expressed using coefficients of balanced equations

Therefore, for moles to energy, -812/1mole CH4 OR -812kJ/ 2mole O2 = -406/ 1mole O2

For products, delta H in kJ/mole (Moles to energy)

-812/ 1mole CO2 OR -812/ 2mole H2O = -406/ 1mole H2O

• The value of delta H depends on what chemical you refer to.
• When converting energy to moles, the formula flips from kJ/1mole to 1mole/kJ.