Chapter 3, Problem 3.2QP

What     are     the     units for     energy commonly     employed in chemistry?

The SI unit of energy is joule (J).  It is also the unit for work and amount of heat. The SI unit for energy is the same as the unit of work because energy is defined via work. The joule (J) named in honor of James Prescott Joule and his experiments on the mechanical equivalent of heat. 1 joule is equal to 1 newton metre.

Joule is comparatively small quantity of energy.  It is defined as the amount of kinetic energy possessed by a 2-kg mass moving at a speed of 1 m/s. 

$Ek=\frac{1}{2}m{u}^2=\frac{1}{2}(2kg){(1m/s)}^2=1kg.m^2/s^2=1J$

Other definition of joule is the amount of energy exerted when a force of 1 newton (N) is given over a distance of 1 meter.

energy capacity to do work W = force × distance kg × m²/s² = Joule = J