Which formula equation represents the burning of sulfur to produce sulfur dioxide?
O S(s) + O2(9) A, 502(9)
O 2H2S(s) + 302(0) — 2H2011) +2502(9)
O 4FeS2 + 1102— 2Fe2O3 + 8502
O 2502(g) + O2(g) _V205, 2503(9)

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.