Homework Help: Chemistry

Posted by Ben on Sunday, September 4, 2011 at 3:41pm.

New problem. Any assistance is greatly appreciated.

22.5 ml of ethanol (density=0.789 g/ml) initially at 7.7 deg. C is mixed with 31.6 ml of water (density=1.0 g/ml) initially at 27.1 deg. C in an insulated beaker. Assuming that no heat is lost, what is the final temperature of the mixture. Express your answer using two significant figures.

22.5ml EtOH 22.5ml x 0.789g/1ml= 17.75 g

31.6ml water 31.6ml x 1g/ml=31.6g

total mass= 49.4 g

This is where I am at a loss. There is no q given. q= mass x SHC x delta temp.

SHC ethanol 2.42 J/g*C

SHC water 4.184 J/g*C

Maybe I am making this more complicated than it should be. Any direction now is appreciated. Since there is no heat lost, do I assume that q=1 or do I just subtract the two temps. 27.1*C - 7.7*C=

Chemistry - bobpursley, Sunday, September 4, 2011 at 4:00pm
The sum of heats gained is zero (some lose heat).

heat gained by ethanol+heatgained by water=0

massethanol*Ceth*(Tf-7.7)+masswater*Cwater*(Tf-27.1)=0
solve for Tf

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