Chemical Forums

Chemistry Forums for Students => High School Chemistry Forum => Topic started by: paytmisop on September 16, 2020, 08:14:48 PM

Title: Thermo Chem
Post by: paytmisop on September 16, 2020, 08:14:48 PM

Please answer this with solution/ explanation

A sample of copper was heated to 120oC and then thrust into 200 g of water at 25.00oC.  The temperature of the mixture became 26.50oC.
1. How much heat in joules was absorbed by the water?
2. The copper sample lost how many joules?
3. What was the mass in grams of the copper sample?

Title: Re: Thermo Chem
Post by: Corribus on September 16, 2020, 08:18:22 PM

Please read the forum rules. You must show work to receive help.

Title: Thermo Chem
Post by: paytmisop on September 16, 2020, 08:32:26 PM

Okay so, I am in a dilemma. The question is: A sample of copper was heated to 120oC and then thrust into 200 g of water at 25.00oC.  The temperature of the mixture became 26.50oC.
1. How much heat in joules was absorbed by the water? (q=1.25 kJ)
2. The copper sample lost how many joules? (Copper lost 1.25 kJ)
3. What was the mass in grams of the copper sample? (m = 34.8 g)

For my c value, I simply subtract 120 by 26.5 to get -93.5. Then I convert 200g into kg which is 0.2Kg for my m. I already know the heat capacity is 4.18 (cuz its water). Somehow I keep getting the question wrong, even though I'm simply plugging in these numbers into the Q=mc T formula. What am I doing wrong?

Title: Re: Thermo Chem
Post by: billnotgatez on September 16, 2020, 10:35:59 PM

@paytmisop
I merged your 2 posts since they deal with the same question.

Title: Re: Thermo Chem
Post by: Borek on September 17, 2020, 03:06:01 AM

Quote from: paytmisop on September 16, 2020, 08:32:26 PM

For my c value, I simply subtract 120 by 26.5 to get -93.5.

That looks more like ΔT. But there are two ΔTs in the problem, and - assuming you are doing the first part of the question (a) it is not the one you should use..

Quote

Then I convert 200g into kg which is 0.2Kg for my m. I already know the heat capacity is 4.18 (cuz its water). Somehow I keep getting the question wrong, even though I'm simply plugging in these numbers into the Q=mc T formula. What am I doing wrong?

Logic looks OK, hard to tell not seeing specific details of your work.

Title: Re: Thermo Chem
Post by: Enthalpy on September 21, 2020, 01:54:58 PM

I agree with 120°C - 26.5°C.
Maybe it's a matter of accurate heat capacity of copper. With 393J/kg/K I get 34.2g.

Temperatures to 0.01K, that's not easy to measure.

Title: Re: Thermo Chem
Post by: DrCMS on September 22, 2020, 05:47:16 AM

Have you tried putting the values in in J rather than kJ?

I get slightly different but similar values to others using 4182J/kg/K for water and 385J/kg/K for copper.