Change in enthalpy equation help
I am working on calculations for a change in enthalpy/Hess's law experiment, we used calorimeters and reacted 100mL of HCl (in excess) with .152g Mg. Our initial temperature was 20.0C and final temperature was 26.5C. We determined that Ccal for the calorimeter was 56 J/C. How do I determine delta H, the change in enthalpy per mole?
I am currently using the formula
delta H= (mc(Tfinal-Tinitial)+Ccal(Tfinal-Tinitial))/n
Where m = mass
c= specific heat, in this case using 4.184J/g*C (as directed by professor)
and n = number of moles
Does my equation look correct?
I calculated n using the mass of the Mg sample and dividing it by the molar mass of Mg
What do I use as the mass for the experiment?
Do I use the mass of the Mg sample?
The mass of the reactants spent in the reaction? This would be taking the number of moles of Mg present and multiplying it by 2 (since two moles of HCl react with 1 mole of Mg) and the multiplying it by the molar mass of Mg.
Or is it the total mass of the stuff in the calorimeter, so the mass of the Mg sample and the mass of the 100mL of 1.0M HCl?
Help would be appreciated, I've been working on this for 20 hours, most of it trying to figure out what to do, I did try talking to our lab professor but he didn't want to help me.
Change in enthalpy equation help
I am working on calculations for a change in enthalpy/Hess's law experiment, we used calorimeters and reacted 100mL of HCl (in excess) with .152g Mg. Our initial temperature was 20.0C and final temperature was 26.5C. We determined that Ccal for the calorimeter was 56 J/C. How do I determine delta H, the change in enthalpy per mole?
I am currently using the formula
delta H= (mc(Tfinal-Tinitial)+Ccal(Tfinal-Tinitial))/n
Where m = mass
c= specific heat, in this case using 4.184J/g*C (as directed by professor)
and n = number of moles
Does my equation look correct?
I calculated n using the mass of the Mg sample and dividing it by the molar mass of Mg
What do I use as the mass for the experiment?
Do I use the mass of the Mg sample?
The mass of the reactants spent in the reaction? This would be taking the number of moles of Mg present and multiplying it by 2 (since two moles of HCl react with 1 mole of Mg) and the multiplying it by the molar mass of Mg.
Or is it the total mass of the stuff in the calorimeter, so the mass of the Mg sample and the mass of the 100mL of 1.0M HCl?
Help would be appreciated, I've been working on this for 20 hours, most of it trying to figure out what to do, I did try talking to our lab professor but he didn't want to help me.
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Related questions
Hi, I am providing all of the information as it is probably needed to answer the last couple of questions. I need help answering the last three boxes.
1. Calculate the heat released into the solution for the 3 reactions, according to Reaction= Ccal*Delta T+ m contents * Cp contents * Delta T.
2. Find the molar heat of reaction for each experiment in units of Kilo-Joules / (mole of Mg) by dividing the heat of reaction by the moles of Mg used.
3. Calculate and record the average molar heat of reaction from the three results.
Thank you for your help.
The Effect of Substrate Concentration on Catalase Activity | |
A. Mass of the empty calorimeter (g): | 18.600g |
B. Initial temperature of the calorimeter (°C): | 21.5C |
C. Maximum temperature in the calorimeter from the reaction (°C): | 34.5C |
D. Calculate delta T by subtracting (b) from (c) (°C) delta T = Tmaximum â Tinitial: | 34.5-21.5 = 13C |
E. Mass of the calorimeter and its contents after the reaction (g): | 68.738g |
F. Calculate the mass of the contents of the calorimeter (g) by subtracting (a) from (e) | 68.738-18.600=50.138g |
G. Calculate the moles of Mg reacted (MW = 24.305 g/mole) | 50.138/24.305=2.0628 moles |
The Effect of Substrate Concentration on Catalase Activity 2 | |
A. Mass of the empty calorimeter (g): | 18.600g |
B. Initial temperature of the calorimeter (°C): | 21.5C |
C. Maximum temperature in the calorimeter from the reaction (°C): | 43.2C |
D. Calculate delta T by subtracting (b) from (c) (°C) delta T = Tmaximum â Tinitial: | 43.2-21.5= 21.7C |
E. Mass of the calorimeter and its contents after the reaction (g): | 68.829g |
F. Calculate the mass of the contents of the calorimeter (g) by subtracting (a) from (e) | 68.829-18.600=50.229g |
G. Calculate the moles of Mg reacted (MW = 24.305 g/mole) | 50.229/24.305=2.066moles |
The Effect of Substrate Concentration on Catalase Activity 3 | |
A. Mass of the empty calorimeter (g): | 18.600g |
B. Initial temperature of the calorimeter (°C): | 21.5C |
C. Maximum temperature in the calorimeter from the reaction (°C): | 51.8C |
D. Calculate delta T by subtracting (b) from (c) (°C) delta T = Tmaximum â Tinitial: | 51.8-21.5= 30.3C |
E. Mass of the calorimeter and its contents after the reaction (g): | 68.921g |
F. Calculate the mass of the contents of the calorimeter (g) by subtracting (a) from (e) | 68.921-18.600=50.321g |
G. Calculate the moles of Mg reacted (MW = 24.305 g/mole) | 50.321/24.305=2.07moles |
Calculate the heat released into the solution for the 3 reactions, according to: Reaction= Ccal*Delta T+ m contents * Cp contents * Delta T | |
Trial 1 | |
Trial 2 | |
Trial 3 |
Find the molar heat of reaction for each experiment in units of Kilo-Joules / (mole of Mg) by dividing the heat of reaction by the moles of Mg used. | |
Trial 1 | |
Trial 2 | |
Trial 3 |
Calculate and record the average molar heat of reaction from the three results. | |
Average |