Question

1- The molar mass and molar heat capacity of aluminum is 27.0 g/mol and 24.3 J/(mol K), respectively. If a 27.0-g Al sample, at 300. K, absorbed 168 J of heat, what is its final temperature?

2- The molar mass and molar heat capacity of aluminum is 27.0 g/mol and 24.3 J/(mol K), respectively. If a 27.0-g Al sample, at 300. K, absorbed 152 J of heat, what is its final temperature?

3- 100. g water, at 20 C, and 100. g copper, at 80 C, are mixed in an insulated calorimeter. Without doing any calculation, predict a reasonable final temperature after thermal equilibrium is reached. Select the best option!

1- 50 C

2- 60 C

3- 100C

4-30 C

Answer #1

1)

mol of Al, n = mass / molar mass

= 27.0 g. /27.0 g/mol

= 1 mol

C = 24.3 J/mol.K

use:

Q = n*C*(Tf-Ti)

168 = 1*24.3*(Tf - 300)

Tf - 300 = 6.9

Tf = 307 K

Answer: 307 K

2)

mol of Al, n = mass / molar mass

= 27.0 g. /27.0 g/mol

= 1 mol

C = 24.3 J/mol.K

use:

Q = n*C*(Tf-Ti)

152 = 1*24.3*(Tf - 300)

Tf - 300 = 6.3

Tf = 306 K

Answer: 306 K

3)

since heat capacity of water is greater than that of copper, final temperature will be closer to initial temperature of water

Answer: 30 C

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