Midterm Q3A

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torialmquist1F
Posts: 49
Joined: Sat Jul 22, 2017 3:00 am

Midterm Q3A

Postby torialmquist1F » Sun Feb 25, 2018 10:41 pm

Calculate the heat (kj) that must be supplied to a 1.4 kg iron pot containing 1.2 kg water in order to raise its temperature from 22 degrees celsius to the boiling point of water. Assume no water evaporates. What percentage of the water was used for heating the water?

What are the steps for solving this problem?

DianaTrujillo2K
Posts: 40
Joined: Fri Sep 29, 2017 7:04 am

Re: Midterm Q3A

Postby DianaTrujillo2K » Sun Feb 25, 2018 10:46 pm

To solve this problem you find the heat needed to raise the temperature of the pot to 100 degrees C and the heat required to raise the temperature of the water to 100 degrees C. You add the heat values to answer the first question. To find the percentage of heat used on the water, you divide the heat required to raise the temperature of the water by the total heat and multiply by 100.

Cassidy 1G
Posts: 54
Joined: Fri Sep 29, 2017 7:07 am

Re: Midterm Q3A

Postby Cassidy 1G » Sun Feb 25, 2018 10:48 pm

q(iron pot) = 14000g * 0.4495 J/(g*degreesC) * (100-22degC) = 6293 J/degC * 78degC = 490854J = 4.90*10^2 kJ
q(water) = (12000g/18.02g/mol) * 75.3J/(K*mol) * (373.15K-295.15K) = 50144.3J/K * 78K = 3.91*10^3 kJ
%heat = q(water)/q(total) = 0.8905 = 89%


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