Question

Please answer the question with explanations of what is happening at each stage. Metallic tin is produced by the reduction of stannic oxide (SnO₂) according to the following reaction:

SnO₂ + 2CO = 2CO₂ + Sn

Stannic oxide crystals are fed to a furnace at 325^oC. Carbon monoxide enters the furnace at 725^oC and 50% in excess. The reduction is complete and the resulting tin is drawn off as a liquid. The gaseous product stream is vented from the furnace at 475^oC.

Assuming no heat losses, calculate the temperature at which the molten tin leaves the furnace.

Data:

Standard (25^oC) heats of formation:

SnO₂ (s)         -138.8 kcal/mol

CO (g)            -26.42 kcal/mol

CO₂ (g)           -94.05 kcal/mol

Specific heat capacities (assume constant):

SnO₂ (s)         16.5 cal/mol K

CO (g)            7.4 cal/mol K

CO₂ (g)           10.6 cal/mol K

Sn (s)              6.5 cal/mol K

Sn (l)               6.6 cal/mol K

Melting point of tin 232^oC

Heat of fusion of tin1.72 kcal/mol

Answer 1

Given Reaction

Sno₂ + 2Co = 2Co₂ + Sn

the system behaves as :

Sno₂ comes from 325C to 25C....

Q = ncpDeltaT = 100 md X 16.5 Cal/md K X (25 - 325) K = - 495 Kcal    ----- 1)

Co comes from - 25 C to 25 C....

Q = nCpDeltaT = 300md X 7.4 cal/md K X (25 - 725) K = - 1554 kcal      ----- 2)

Reaction occurs...

Q = nDeltaTi_rXn = 100md X 3.54 kcal/mol

= 354 kcal     ------ 3)

Exit gases taken to 475 C from 25 C.

For CO_{2 .....}

Q = nCpDeltaT

= 100 mol X 7.4 cal/mol K X (425 - 25) K

= 296 kCal     ------ 4)