A 97 g sample of gold at 785oC is dropped into
323 g of water, which has an initial temperature
of 15oC. If gold has a specific heat of 0.129 J/goC,
what is the final temperature of the mixture?
A 97 g sample of gold at 785oC is dropped into 323 g of water, which has an initial
temperature of 15oC. If gold has a specific heat of 0.129 J/goC, what is the final
temperature of the mixture? Assume that the gold experiences no change in state
of matter.
-LOST heat (metal) = GAINED heat (water)
- [(s ) (mass) (DT)] = (s ) (mass) (DT)
Au
H2O
-[(0.129 J/goC)(97 g)(Tf - 785oC)] = (4.184 J/goC)(323 g)(Tf -15oC)
-[(12.5J/oC)(Tf - 785oC)]= (1.35x 103J/oC)(Tf -15oC)
(1.35x 103J/oC)
(1.35x 103J/oC)
-[(0.009259 )(Tf - 785oC)]= Tf -15oC
- 0.009259 Tf + 7.268 oC = Tf -15oC
22.268 oC = 1.009259Tf
Tf = 22.0637oC → 22oC
Two metals of equal mass with different heat
capacities are subjected to the same amount of
heat. Which undergoes the smallest change in
temperature?
1) The metal with the higher heat capacity.
2) The metal with the lower heat capacity.
3) Both undergo the same change in temperature.
4) You need to know the initial temp of the metals.
Convert 5.721 kcal to Joules
The reaction pictured in the graph
below is ______________.
Energy
Products
Reactants
Reaction progress
Exothermic Reaction
Reactants  Products + Energy
Energy of reactants
Energy
Energy of products
Reactants
-DH
Products
Reaction Progress
When heat flows into a system from the
surroundings, this process is ______
Cooking an egg is __________
1) Exothermic
2) Endothermic
Formation of snow in clouds is ______
1) Exothermic
2) Endothermic
Water condensing on the outside
of a cold glass on a hot day:
1. Exothermic
2. Endothermic
4Fe + 3O2  2Fe2O3 ΔH= -1652 kJ
• How much heat is
released when
2.00g of O2 is
reacted?
Consider the following standard heats of formation:
P4O10(s) = –3110 kJ/mol
H2O(l) = –286 kJ/mol
H3PO4(s) = –1279 kJ/mol
Calculate the change in enthalpy for the following:
P4O10(s) + 6H2O(l)  4H3PO4(s)
Consider the following numbered processes:
1. A  2B
2. B  C + D
3. E  2D
DH for the process A  2C + E is
1) DH1 + DH2 + DH3
2) DH1 + DH2
3)DH1 + DH2 – DH3
4) DH1 + 2DH2 – DH3
5) DH1 + 2DH2 + DH3
A 0.0459kg sample of a metal is heated to
95.5°C and then placed in a calorimeter
containing 120.0 g of water (s = 4.18 J/g°C) at
21.6°C. The final temperature of the water is
24.5°C. Which metal was used?
1)
2)
3)
4)
Aluminum (s = 0.89 J/g°C)
Iron (s = 0.45 J/g°C)
Copper (s = 0.20 J/g°C)
Lead (s = 0.14 J/g°C)
The heat combustion of acetylene, C2H2(g), at
25°C is –1299 kJ/mol. At this temperature,
ΔHf° values for CO2(g) and H2O(l) are –393
and
–286 kJ/mol, respectively. Calculate ΔHf° for
acetylene.
1)
2)
3)
4)
5)
2376 kJ/mol
625 kJ/mol
227 kJ/mol
–625 kJ/mol
–227 kJ/mol