Search 79,001 tutors
FIND TUTORS
Ask a question
0 0

Calorimeter Help!!

A researcher studying the nutritional value of a new candy places a 3.40 gram sample of the candy inside a bomb calorimeter and combusts it in excess oxygen. The observed temperature increase is 2.36 C. If the heat capacity of the calorimeter is 46.80 kJ*K-1, how many nutritional calories are there per gram of the candy?
Tutors, please sign in to answer this question.

1 Answer

Harley,
 
See the answers to your other questions and
 
Remember the equation
 
ΔH = -Ccal x ΔT.
 
Hints:
 
1) make sure ΔT in in K
2) 1 nutritional calorie = 4.2 kJ
3) give the answer on a per gram basis of candy
 
I think you can take it from here!!
 
 
 

Comments

Carol,
 
Unfortunately, I am still not coming up with the correct answer. I don't know if I am calculating wrong or what?
 
Harley
Do you want to share your work so far?  I may be able to help if I see what you've tried.
I multiplied 46.80 x 2.36 then took that answer and converted calories. And finally divided it by 3.40.
Harley, Here's what I get
 
ΔH = -Ccal x ΔT
        - 46.80 kJ/K x 2.36 K = -110.448 kJ
 
convert to nutritional calories
-110.48 kJ (1 Calorie/4.2 kJ) = -26.3 Calorie
 
Calories per gram
-26.3 C/ 3.40 g = -7.73 Calorie/gram
 
Did you get something different?
working on a similiar problem.... only question I have is the Calorie being negative... I get that the Ccal was -... but trying to understand the negative behind a calorie....
 
Steven,
 
When reporting food Calories, the negative sign is omitted.  In thermochemistry the negative sign indicates that the reaction is exothermic meaning energy is released.  Since we obviously eat food in order to get energy from it, the negative sign isn't meaningful.  
 
Also note that a food Calorie (with a capital C) equals 1000 thermochemical calories.