Which of the following is not a redox reaction?
a. h2o(l) + nh3(g) latex: \longrightarrow nh4+(aq) + oh–(aq)
b. 2h2(g) + o2(g) latex: \longrightarrow 2h2o(l)
c. zn(s) + h2so4(aq) latex: \longrightarrow znso4(aq) + h2(g)
d. feso4(aq) + k2cr2o7(aq) + 7h2so4(aq) latex: \longrightarrow cr2(so4)3(aq) + 3fe2(so4)3(aq) + k2so4(aq) + 7h2o(l)
e. cl2(g) + 2kbr(aq) latex: \longrightarrowbr2(l) + 2kcl(aq)

the answer is c.the valence of the atoms combine .

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.