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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: oceanmd on April 17, 2008, 11:13:53 PM

Title: Final temperature of a mixture
Post by: oceanmd on April 17, 2008, 11:13:53 PM

Please check the problem below and explain if it is wrong. Thank you.

What is the final temperature of a mixture of chromium metal when 50.0 grams of chromium at 15 degrees C ( specific heat = 0.448 J/g C) is added to 25 mL of water (specific heat = 4.18 J/ g C) at 45 degrees C?

This is what I think.  0.448 x 50 x (x-15) = -(4.18 x 25 x (x-45)), the answer is 40 degrees C

I need the minus before the second part of the equation because water releases heat, so the number is negative, and to make the equation work I need minus. Is this correct? Is there a better explanation?

Thank you

Title: Re: Final temperature of a mixture
Post by: phmonkey on April 18, 2008, 02:03:47 AM

0.448 x 50 x (x-15) = -(4.18 x 25 x (45-x)),
i believe its that, because 45 degrees is going down

Title: Re: Final temperature of a mixture
Post by: phmonkey on April 18, 2008, 02:07:11 AM

i switched x and 45 around in case u didnt see it

Title: Re: Final temperature of a mixture
Post by: ARGOS++ on April 18, 2008, 03:44:29 AM

Dear Phmonkey;

The swap of x and 45 you did correct.

Quote from: phmonkey on April 18, 2008, 02:03:47 AM

0.448 x 50 x (x-15) = -( 4.18 x 25 x (45-x) )

But do you really believe that now both are required?

Good Luck!
                    ARGOS⁺⁺