An atom’s oxidation number changes from –2 to –5. Was the atom oxidized or reduced, and how many electrons were required for the change? A. Oxidized, 2 electrons
B. Oxidized, 3 electrons
C. Reduced, 2 electrons
D. Reduced, 3 electrons
E. None of the Above

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.