Compared to a 0.1 m aqueous solution of nacl, a 0.8 m aqueous solution of nacl has a
(1) higher boiling point and a higher freezing point
(2) higher boiling point and a lower freezing point
(3) lower boiling point and a higher freezing point
(4) lower boiling point and a lower freezing point

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.