Given the balanced equation representing a reaction:
cl2(g) ==> cl(g) + cl(g)
what occurs during this change?
(1) energy is absorbed and a bond is broken.
(2) energy is absorbed and a bond is formed.
(3) energy is released and a bond is broken.
(4) energy is released and a bond is formed.

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.