Transcript Thermo Review

Thermo Review
0. True or false: Energy transfers occur only
during chemical reactions
False
1. For an endothermic reaction, the overall
enthalpy change is
a. Negative
b. Positive
c. Does not have a sign only a unit
2. To write the alternate form of the following
reaction H2 + Cl2  2HCl H = - 185 kJ
a. Change the sign
b. Reverse the equation
c. Write the energy as a reactant
d. Write the energy as a product
H2 + Cl2  2HCl H = - 185 kJ
3. What mass of Chlorine would be required to
release 925 kJ of energy?
a. cannot be determined
b. 5 grams
c. 177.25 grams
d. 354.5 grams
4. The standard enthalpy change for a
reaction can be found by which of
the following
a. sum of enthalpies of reactants minus sum of
enthalpy of products, excluding coefficients
b. sum of enthalpies of reactants minus sum of
enthalpy of products, including coefficients
c. sum of enthalpies of products minus sum of
enthalpy of reactants, excluding coefficients
d. sum of enthalpies of products minus sum of
enthalpy of reactants, including coefficients
5. Specific heat capacity is…
a. the energy required to form a compound
b. the energy needed to raise a substance one
degree celsius
c. the energy needed to raise the temperature
of one gram of substance one degree celsius
d. Always greater than 1
6. How much heat is given off by a 50.0 g sample
of copper when it cools from 80.0 to 50.0C?
Specific heat of copper is 0.382 J/gC
a. - 573 J
b. 573 J
c. 573 kJ
d. - 573 kJ
O2(g) + 2SO2 (g)  2SO3 (g)
7. Determine the change in enthalpy of the
reaction using the standard heats of formation
a. 296.8 kJ
b. -395.7 kJ
c. -791.4 kJ
d.- 197.8 kJ
8. Iron has a specific heat of 0.446 J/gC. When
a 7.55 g piece of iron absorbs 10.33 J of heat.
If it was originally at room temp. (22.0C),
what is the final temperature?
a. 3.07 C
b. 18.93 C
c. 25.1 C
9. Along which portions of the
heating/cooling curve is there no
temperature change?
a)
b)
c)
d)
Solid and Liquid phase
Solid, Liquid and Gas phase
Vaporization and Fusion
Solid and Gas phase
10. What happens to the temperature
of the water in the calorimeter when a
heated metal is put inside?
a)
b)
c)
d)
Water temperature goes up
Water temperature goes down
Water temperature stays the same
Water temperature goes down and then up
11. If heat is absorbed by a chemical
system, then the surroundings have to
a) Release heat
b) Absorb heat
c) Stay at the same temperature
12. Based on what law are we able
to determine the specific heat of
an unknown metal?
a)
b)
c)
d)
Law of Conservation of Matter
Law of Conservation of Energy
Combined Gas Law
Avogadro’s Law
13. If the water in a calorimeter
absorbs 526J of heat, how much heat
did the object that was placed inside
release?
a)
b)
c)
d)
263J
526J
-263J
-526J
14. Endothermic reactions:
a)
b)
c)
d)
Do not involve heat
Absorb heat
Release heat
Happen instantaneously
15. Calculate the amount of heat
needed to raise 42.3g sample of
water from -35.7ºC to 112.0ºC
a)
b)
c)
d)
3160J
26,140J
132, 000J
95,600J