Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: mr cool on May 04, 2009, 06:02:18 PM
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Lab data:
Aluminum---Copper---Alloy (pennies)
Temp of water---------------- 90.0 *C---91.0*C----91.0*C
Final calorimeter temp-------29.3. *C---29.8*C----29.7*C
Initial calorimeter temp-------24.6 *C---24.8*C----24.5*C
In this lab we setup a system wbere a testube full of aluminum was heated up with water in a 250 ml beaker surrounding it. But thats irrelevent...
Onto the questions....
Pure samples....
1: calculate the change in temp of both metals....
29.3 -24.6= 4.7 *C Change-----Aluminum
29.8 - 24.8 = 5.0 *C Change----Copper
2: calculate the heat gained by the water in each trial ...
How would i do this?
3: calculate the specific heat of both metals (cant do it without help on number 2?)
4:the accepted theoretical value of copper is 0.389 J/g C. And zinc is 0.388 J/g C. Determine your perceny error for your copper trials. (i can do this easily if i had help with number 2)
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Dear mr cool;
What is the mass of water of the calorimeter?? It is required!
For 2.:
Use: q = m * c * ∆T For cwater see on:
http://www.engineeringtoolbox.com/water-thermal-properties-d_162.html
For 3.:
Use: q = c * m * ∆T and: Qgain = Qloss.
(Search the forums; there are several similar/identical questions.)
Good Luck!
ARGOS++
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Dear mr cool;
What is the mass of water of the calorimeter?? It is required!
For 2.:
Use: q = m * c * ∆T For cwater see on:
http://www.engineeringtoolbox.com/water-thermal-properties-d_162.html
For 3.:
Use: q = c * m * ∆T and: Qgain = Qloss.
(Search the forums; there are several similar/identical questions.)
Good Luck!
ARGOS++
Water used = 50.0 ml so 50.0 g.
So m * C * temp change
50.0 g * C * 29.3-24.6 = heat gained? What do i put as C?
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Dear mr cool;
From the link I gave you: cWater(l) = 4.187 J °K-1 g-1
Good Luck!
ARGOS++
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So i did 50.0 * 4.187 * 4.7 = 983.945 ... That doesnt seem right.
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Dear mr cool;
But it is right for 4.7°K, - if you add the unit Joule. Check for the units.
Good Luck!
ARGOS++
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Oh lol, silly me, i forgot heat is not equal to temperature gained :)
Yea, 900 J is more logical now, 983.94 J / g * C... Correct?
Then, 50.0g * 4.187 (C?, not sure on units). * 5.0 = 1046.75 J/ g *C
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Dear mr cool;
No! – The unit is only Joule! Do the calculation with all units and cancel them out!
But the values are correct.
Good Luck!
ARGOS++
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Dear mr cool;
No! – The unit is only Joule! Do the calculation with all units and cancel them out!
Good Luck!
ARGOS++
50.0 g * 4.187 *4.7 *C. I dont see how thise are canceling
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Dear mr cool;
What did I give you for units for Cwater?:
From the link I gave you: cWater(l) = 4.187 J °K-1 g-1
Good Luck!
ARGOS++
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Ok well now #3 is purplexing me.
In my book it says change in heat energy = specific heat of sample * mass of sample * change in temp of sample.
But i have a feeling he wants us to switch up this equation a bit because we dont have specific heat.
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Dear mr cool;
For 3.) you have to solve the formula q = c * m * ∆T for cmetal and use the correct values for mass and ∆T.
Good Luck!
ARGOS++
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Dear mr cool;
For 3.) you have to solve the formula q = c * m * ∆T for cmetal and use the correct values for mass and ∆T.
Good Luck!
ARGOS++
What is cmetal
C * 7.8229 * 29.3 - 24.6. ?
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Dear mr cool;
Do you know what means to solve an equation for a given parameter?
If yes, - then please repeat:
For 3.) you have to solve the formula q = c * m * ∆T for cmetal and use the correct values for mass and ∆T.
c = cmetal is the value you have to find/calculate!
Am I correct if I assume that 7.8229 mean the mass of aluminium?
And that (4.7°K) is not the temperature difference of aluminium!
Good Luck!
ARGOS++
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29.3 - 24.6 = 4.7 = temp change of aluminum.
And i have no clue about the rest ofthe post, this is impossible.
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Dear mr cool;
If you don’t know how to re-arrange the equation for c, then I can’t help you.
Then you have to wait for somebody else who can help you better than I.
(∆T for aluminium is 90.0°C – 29.3°C and not 4.7°K.)
Good Luck!
ARGOS++
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Sorry, mistakenly deleted your post.
29.3 - 24.6 = 4.7 = temp change of aluminum.
And i have no clue about the rest ofthe post, this is impossible.
No. But this is simple algebra, you really should know how to rearrange formulas.