Honors Chemistry Test #8: Thermochemistry and
Phase ChangeName
Date
Period
/80 POINTS
Multiple Choice (1 point each)
Identify the choice that best completes the statement or answers the question.
____1.According to the kinetic-molecular theory, particles of matter
a. / are in constant motion. / c. / have different colors.b. / have different shapes. / d. / are always fluid.
____2.The intermolecular forces between particles are
a. / weaker in solids than in liquids.b. / stronger in gases than in solids.
c. / equal in strength in gases and in liquids.
d. / stronger in liquids than in gases.
____3.Which term best describes the process by which particles escape from the surface of a nonboiling liquid and enter the gas state?
a. / sublimation / c. / surface tensionb. / evaporation / d. / aeration
____4.Which of these can happen due to decreasing the average energy of a liquid's particles?
a. / vaporization / c. / a random arrangementb. / evaporation / d. / freezing
____ 5. According to the figure below, what is the most volatile substance shown?
a. / benzene / c. / tolueneb. / water / d. / aniline
____ 6. Enthalpy change is the
a. / pressure change of a system at constant temperature.b. / entropy change of a system at constant pressure.
c. / temperature change of a system at constant pressure.
d. / amount of energy absorbed or lost by a system as energy is the form of heat during a process at constant pressure.
____7.If the rate of evaporation from the surface of a liquid exceeds the rate of condensation,
a. / the system is in equilibrium.b. / the liquid is boiling.
c. / energy as heat is no longer available.
d. / the concentration of the vapor is increasing.
____8.The triple point of a substance is the temperature and pressure conditions at which
a. / density is greatest.b. / states of a substance coexist at equilibrium.
c. / equilibrium cannot occur.
d. / kinetic energy is at a minimum.
____9.At a given temperature, different liquids will have different equilibrium vapor pressures because
a. / the energy of the particles is the same for different liquids.b. / diffusion rates differ for the liquids.
c. / the attractive forces between the particles differ among liquids.
d. / they cannot all be in equilibrium at once.
____10.A volatile liquid
a. / has strong attractive forces between particles.b. / evaporates readily.
c. / has no odor.
d. / is ionic.
____11.What is the process of a substance changing from a solid to a vapor without passing through the liquid phase?
a. / condensation / c. / sublimationb. / evaporation / d. / vaporization
____12.At pressures greater than 1 atm, water will boil at
a. / a temperature higher than 100ºC. / c. / 100 ºC.b. / a temperature lower than 100 ºC. / d. / 4 ºC.
____13.Why would a camper near the top of Mt.Everest find that water boils at less than 100ºC?
a. / There is greater atmospheric pressure than at sea level.b. / The flames are hotter at that elevation.
c. / There is less atmospheric pressure than at sea level.
d. / The atmosphere has less moisture.
____14.During boiling, the temperature of a liquid
a. / remains constant. / c. / decreases.b. / increases. / d. / approaches water's boiling point.
____15.How does the molar enthalpy of fusion of ice compare with the molar enthalpy of vaporization of water?
a. / the molar enthalpy of fusion is relatively larger than the molar enthalpy of vaporization.b. / the molar enthalpy of vaporization is relatively larger than the molar enthalpy of fusion.
c. / they are about the same as far as amount of energy.
d. / It is about the same as that of colorless solids.
____16.The greater the average kinetic energy of the particles in a sample of matter,
a. / the higher the temperature is.b. / the lower the temperature is.
c. / the more energy is absorbed by the sample in the form of heat.
d. / the less energy is released by the sample in the form of heat.
____17.In a calorimeter, the energy content of a substance is calculated from measurement of the temperature change in a known mass of
a. / iron. / c. / water.b. / air. / d. / steel.
____18.Energy is measured in units of
a. / grams. / c. / pounds.b. / joules. / d. / kelvin.
____19.The energy transferred between samples of matter because of a difference in their temperatures is called
a. / heat. / c. / chemical kinetics.b. / thermochemistry. / d. / temperature.
____20.What is the energy required to raise the temperature of 1 g of a substance by 1°C or 1 K?
a. / specific heat / c. / heat capacityb. / heat energy / d. / enthalpy of formation
____21.The quantity of energy released or absorbed as heat during a chemical reaction is called the
a. / temperature. / c. / entropy.b. / enthalpy of reaction. / d. / free energy.
____22.Which of the equations below is an example of a thermochemical equation?
a. /b. /
c. /
d. /
____23.In an endothermic reaction, the total energy at the beginning of the reaction is
a. / greater than the total energy at the end of the reaction.b. / less than the total energy at the end of the reaction.
c. / equal to the total energy at the end of the reaction.
d. / None of the above
____24.What is the energy released or absorbed as heat when one mole of a compound is produced by combination of its elements?
a. / enthalpy of formation / c. / free energyb. / enthalpy of combustion / d. / entropy
____25.The enthalpy of formation of an element is
a. / negative.b. / positive.
c. / zero.
d. / negative or positive, depending on which element.
____26.Glycerol boils at a slightly higher temperature than water. This reveals that glycerol's attractive forces are
a. / nonexistent. / c. / the same as those of water.b. / weaker than those of water. / d. / stronger than those of water.
____27.Ice melting is an example of a(n)
a. / exothermic reaction. / c. / endothermic reaction.b. / negative entropic reactions. / d. / catalyzed reaction.
____28.As ice melts, the water molecules
a. / go from a well-ordered phase to a less-ordered phase.b. / go from a less-ordered phase to a more-ordered phase.
c. / stay ordered the same as in ice.
d. / None of the above
Problem – Show work, units and correct number of significant figures in the answer for full credit.
29. Given that water has a molar enthalpy of vaporization of 40.79 kJ/mol, how many grams of water could be vaporized by 623 J?(4 points)
30. Use the table of heats of formation to determine ΔH for the reaction represented by the equation.
2C2H6 (g) + 7O2 (g) → 4CO2 (g) + 6H2O (g) (4 points)
31. At the beach, why does the sand heat up and cool faster than water? (4 points)
32. Which has more heat – a cup of boiling water (100oC) or a bucket of water at 50oC? Why? (2 points)
33.You want to determine the specific heat of an unknown metal using a foam calorimeter with water, a thermometer, a hot plate, and a balance. You collect the following data:
Mass of water: 52.3 g
Mass of metal: 84.1 g
Initial temperature of water: 21.6 oC
Initial temperature of metal: 97.5 oC
Final temperature of metal and water: 24.9 oC
Using Q = mcΔT, find the specific heat of the unknown metal. (8 points). The specific heat of liquid water is 4.18 J/goC
34. Explain the relationships between volatility, evaporation rates, flammability and intermolecular forces in a liquid. (2 points)
35. Why do we normally not see dry ice (CO2) in the liquid form? (1 point)
36. Classify the following phase changes as exothermic or endothermic: (1 point each)
a) freezing
b) condensing
c) vaporizing
37 . Using Hess’s Law, find the ΔH for the reaction below, given the following reactions and subsequent ΔH values: SHOW CHANGES IN ENTHALPY TO RECEIVE CREDIT.(6 points)
C3H8 (g) + 5 O2 (g) -----> 3 CO2 (g) + 4 H2O(g) DESIRED
GIVEN:
3C (s)+ 4 H2 (g) ------> C3H8 (g) ΔH = - 103.8 kJ
2 H2(g) + O2 (g) ------> 2H2O (g)ΔH = -484 kJ
C (s) + O2 (g) ------> CO2 (g)ΔH = -393.5 kJ
38.Consider the heating curve of water below. (2 points each)
a)Why are (b) and (d) flat?
b)What does (c) represent?
39. Consider the phase diagram of water below: (2 points each)
a) What is the state of water at 2 atm and 50?
b) What phase change will occur if the temperature is lowered from 80C to -5C at 1 atm?
c) What is meant by “normal freezing point?”
Use the following energy constants of water to solve the phase change problem below:(8 points total)
334 J/gHeat of fusion (melting or freezing)
2260 J/gHeat of vaporization (evaporating or condensing)
2.1 J/g∙CSpecific heat of solid water
4.18 J/g∙CSpecific heat of liquid water
1.84 J/g∙CSpecific heat of gaseous water
40.
a)How many Joules are required to heat 54.2 grams of ice from -21 degrees Celsius to 125 degrees Celsius?
b) How many Joules are required to heat 43.6 grams of ice at 0.0degrees Celsius to 86.2 degrees Celsius?