Unit 12 Review Answers 1-19 at the end of the review
1. Looking at the graph below, label each letter:
A
B
C
D
2. Label the following parts of the energy diagram: Reactants, products, activated complex,
activation energy, and enthalpy (delta H).
3. What is the energy of the reactants
4. What is the energy of the products
5. What is the energy of the activated complex
6. What is the Ea?
7. What is the delta H?
8. Is this energy diagram endothermic or exothermic? What two ways can you use to identify this?
.
9.
10.
11.
12.
13.
Identify the temperature range that indicates a solid being heated
Determine the melting point (freezing point) of the substance
Compare the boiling point of this substance to the boiling point of water (100˚C).
Label the graph below with: Liquid, solid, and vapor
See chart below: As the temperature goes from 0 to 500co what phase change is
happening(melting,sublimation, vaporization,condensation or freezing
14. What temperature is the triple point/melting point/
C3H8(g) + 5 O2
H2O(l) ΔH = -2219.2 kJ
15. The heat of formation of any element in its standard (natural) state is…
a. 1 kJ/mol
b. 0 kJ/mol
c. 4.184 kJ/mol
d. 100 kJ/mol
16. Determine the correct way to write the equation above
a.
g) + 4 H2O(l) + 2219.2 kJ
b.
c.
d. As an endothermic reaction: C3H8(g) + 5 O2(g
17. During the lab a piece of hot metal was placed in a can of water. Choose the best answer of
what happened:
a. The water absorbed the heat making it endothermic with a -
H, and the metal a
+ H
b. The metal absorbs the heat and has a - H, water is exothermic
c. The water absorbs the heat and has a + H while the metal has a - H
d. There was no heat transfer
18. If the change in heat is negative, the heat is __________ the system and is ___________.
19. Based on the specific heat capacities listed below, which substance would be able to absorb the
most heat in 10 minutes? Assume you have 10.0 grams of each sample.
Metal
Aluminum
Brass
Copper
Steel
Cp (J/gC
0.900
0.380
0.386
0.470
20. For phase changes of water:
ΔHvap = 40.79 kJ/mol
ΔHfus = 6.009 kJ/mol
21. How much energy is required to boil 32.00 moles of water at 100.0 ˚C (Ans: 1305.28)
22. How much energy is released when 20.0 grams of water are frozen at 0 ˚C? (Ans: -6.67)
23. A 15.75-g piece of iron absorbs 1086.75 joules of heat energy, and its temperature changes from
25°C to 175°C. Calculate the specific heat capacity of iron. (Answer is 2.17 j/gCo)
24. How many joules of heat are needed to raise the temperature of 10.0 g of aluminum from 22°C
to 55°C, if the specific heat of aluminum is 0.90 J/g°C? (297J)
25. 100.0 g of 4.0°C water is heated until its temperature is 37°C. If the specific heat of water is 4.18
J/g°C, calculate the amount of heat energy needed to cause this rise in temperature (13794)
26. How many Joules of energy are required to raise the temperature of 75.00 grams of water from
20.00˚C to 50.00˚C? The specific heat of water is 4.184 J/g˚C. (9405)
27. Photosynthesis changes __________energy into ___________energy
a. Radiant/chemical
b. Chemical/radiant
c. Chemical/electrical
28. The law of conservation of energy states that energy cannot be ___________ or ____________.
a. Released/chemical
b. Created/destroyed
c. Used up/ lost
Answers:
1) Parts of the graph
a. A= Potential Energy of Reactans
b. B= Ea (activation Energy)
c. C= Activated Complex
d. D= Potential energy of Products
2) Use your checklists for the labels
3) 80
4) 160
5) 240
6) 160
7) 80
8) Endothermic. Products have more energy than reactants. Delta H is +
9) 30-55
10) 55
11) Lower than water. It is 90oC
12) Label using the checklist
13) Vaporization
14) 96oC
15) B (it is ZERO)
16) A
17) C
18) Leaving…exothermic
19) Brass