Let\'s say we have two 1 kg blocks of metal. One is aluminum and the other is ir
ID: 971164 • Letter: L
Question
Let's say we have two 1 kg blocks of metal. One is aluminum and the other is iron. Initially, both blocks are at 25 degree C. How much heat must be added to each block to raise each block's temperature to 350 degree C? If the two heated blocks are then placed in the same insulated container in which the blocks are in thermal communication with each other, what is the final temperature of each block after equilibrium is reached? List any assumptions you make for this simple analysis. Let's say that only the aluminum block has been heated to 350 degree C while the iron block was kept at 25 degree C. If these two blocks are then placed in the same insulated container in which the blocks are in thermal communication with each other, what is the final temperature of each block after equilibrium is reached? List any assumptions you make for this simple analysis. d. Now reverse the situation described in part c. above. The aluminum block is kept at 25 degree C while the iron block is heated to 350 degree C prior to placing both blocks in the insulated container. What is the final temperature of each block after equilibrium is reached? List any assumptions you make for this simple analysis.Explanation / Answer
3 - Heat of reaction
a. Heat q = mCpdT
For 1 kg iron
q1 = 1000 g x 0.450 J/g.oC x 325 oC = 146.250 kJ
For 1 kg Aluminium
q2 = 1000 g x 0.900 J/g.oC x 325 oC = 292.500 kJ
b. Let the final temperature be Tf
q1 = q2
1000 g x 0.450 J/g.oC x (Tf - 325) oC = 1000 g x 0.900 J/g.oC x (Tf - 325) oC
450Tf - 146250 = 900Tf - 292500
450Tf = 146250
Tf = 325 oC
c. If Al is heated to 350 oC, Fe at 25 oC
q1 = q2
1000 g x 0.450 J/g.oC x (Tf - 25) oC = 1000 g x 0.900 J/g.oC x (350 - Tf) oC
450Tf - 11250 = 315000 - 900Tf
1350Tf = 326250
Tf = 241.666 oC
d. If Fe is heated to 350 oC, Al at 25 oC
q1 = q2
1000 g x 0.450 J/g.oC x (350 - Tf) oC = 1000 g x 0.900 J/g.oC x (Tf - 25) oC
157500 - 450Tf = 900Tf - 22500
1350Tf = 180000
Tf = 133.333 oC
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