1. Calorimetry

2. Calorimeter qsys = qwater + qcal + qrxn qsys = 0 qrxn = - (qwater)
Reaction at Constant P
DH = qrxn
qsys = qwater + qcal + qrxn
qsys = 0
qrxn = - (qwater)
No heat enters or leaves!

3. Specific heat at constant pressure
Calculating heat
Absorbed or released
𝑞=𝑚𝑐∆𝑇
Change in temperature
𝑇 𝑓 − 𝑇 𝑖
Unit: C
Heat
Unit: J or kJ
Mass
Unit: g
Specific heat at constant pressure
J/gC

4. Specific Heat = c
Specific heat of a substance is the amount of heat required to raise the temperature of one gram of that substance by one degree Celsius.
Unit for specific heat is J/goC

5. Heat capacity
The amount of heat required to raise the system’s temperature by one Celsius.

6. Each substance has a different specific heat
The lower the specific heat the lower the amount energy is required to raise its temperature.

7. Example 1
If the temperature of 56.6g of ethanol increases from 45.0°C to 80.0°C, how much heat has been absorbed by the ethanol? Specific heat of ethanol =2.44J/g°C

8. Example 2
A 4.00g sample of a substance was heated from 274K to 314K and absorbed 32J of heat, what is the specific heat of the substance?

9. Example 3
If 98,000 J of energy are added to 6200 g of water at 14.0C, what will the final temperature of the water be? Specific heat of water = J/gC

10. Example 4
A 45.0g sample of metal is placed in boiling water until its temp. is 100.0C. a calorimeter contains 100.0g of water at a temp of 24.4C. the metal sample is removed from the boiling water and immediately placed in water in the calorimeter. The final temp of the metal and water in the calorimeter is 34.9C. assuming that the calorimeter provides perfect insulation, what is the specific heat of the metal?

11. Example 5
240g of water (initially at 21C) are mixed with an unknown mass of ion (initially at 501C). When thermal equilibrium is reached, the system has a temperature of 42 C. find the mass if the iron. Specific heat of iron = J/gC

12. Example 6
240g of water (initially at 21C) are mixed with an unknown mass of ion (initially at 501C). When thermal equilibrium is reached, the system has a temperature of 42 C. find the mass if the iron. Specific heat of iron = J/gC

13. Example 7
Determine the final temperature when a 25.0g piece of iron at 85.0C is placed into 75.0 grams of water at 20.0C.