× Didn't find what you were looking for? Ask a question
Top Posters
Since Sunday
5
o
5
4
m
4
b
4
x
4
a
4
l
4
t
4
S
4
m
3
s
3
New Topic  
oblique101 oblique101
wrote...
Posts: 27
Rep: 0 0
9 years ago
I'm trying to the final temperature for the following equation:

(10.0g)(0.129 J/gC)(Tfinal-18.0 C)+(20.0g)(0.444J/gC)(Tfinal-55.6 C)=0

(C= celsius Idk how to put the sign)

The answer is 50.83 C but when I do the calculations following the sig figs rules I get 50.85?! Are we supposed to ignore sig fig rules in calorimetry?If so, why 4 sig figs? HELP*!
Read 834 times
5 Replies

Related Topics

Replies
wrote...
9 years ago
This minute difference by .02 should not cause you to get an answer correct. Your answer is fine with 4 sig figs.
wrote...
Valued Member
On Hiatus
9 years ago
(10.0g)(0.129 J/gC)(Tfinal-18.0 C)+(20.0g)(0.444J/gC)(Tfinal-55.6 C)=0 <=>
1.29*(Tfinal-18.0)+ 8.88*(Tfinal-55.6)=0 <=>
1.29*Tfinal -23.22 + 8.88*Tfinal -493.728=0 <=>
10.17Tfinal = 516.948
Tfinal= 50.83C

I can't understand how you got 50.83. Maybe some calc mistake?
oblique101 Author
wrote...
9 years ago
(10.0g)(0.129 J/gC)(Tfinal-18.0 C)+(20.0g)(0.444J/gC)(Tfinal-55.6 C)=0 <=>
1.29*(Tfinal-18.0)+ 8.88*(Tfinal-55.6)=0 <=>
1.29*Tfinal -23.22 + 8.88*Tfinal -493.728=0 <=>
10.17Tfinal = 516.948
Tfinal= 50.83C

I can't understand how you got 50.83. Maybe some calc mistake?
(10.0g)(0.129 J/gC)(Tfinal-18.0 C)+(20.0g)(0.444J/gC)(Tfinal-55.6 C)=0 <=>
1.29*(Tfinal-18.0)+ 8.88*(Tfinal-55.6)=0 <=>
1.29*Tfinal -23.22 + 8.88*Tfinal -493.728=0 <=>
10.17Tfinal = 516.948
Tfinal= 50.83C

I can't understand how you got 50.83. Maybe some calc mistake?

Shouldn't 1.29 * -18.0= -23.2? And, 8.88 *-55.6 = -494? That is what I did ;/
wrote...
Valued Member
On Hiatus
9 years ago
I figured you might did something like that. But, we usually make the rounding at the end when we get the final result. Besides, didn't you said you wanted 4 significant figures? That means, you need number with 4 figures. So, even at this point, 1.29 * -18.0= 23.22 doesn't that have 4 significant figures?

But anyways, as I said, you usually do the rounding when you find the final result (except if you encounter calculation problems, so you decide to simplify some other numbers as well)
oblique101 Author
wrote...
9 years ago
I figured you might did something like that. But, we usually make the rounding at the end when we get the final result. Besides, didn't you said you wanted 4 significant figures? That means, you need number with 4 figures. So, even at this point, 1.29 * -18.0= 23.22 doesn't that have 4 significant figures?

But anyways, as I said, you usually do the rounding when you find the final result (except if you encounter calculation problems, so you decide to simplify some other numbers as well)

I never said I wanted 4 significant figures o-O My professor is making me paranoid with significant figures because he applies the rules as he goes through the calculation and not at the end. But I'll follow your advice because it sounds more reasonable.
New Topic      
Explore
Post your homework questions and get free online help from our incredible volunteers
  1110 People Browsing
Related Images
  
 9
  
 4416
  
 88
Your Opinion
Which of the following is the best resource to supplement your studies:
Votes: 249