AP Chemistry Unit 5
According to the first law of thermodynamics, the energy of the universe is constant. Does this mean that DeltaE is always equal to zero?
C. No, DeltaE does not always equal zero because it refers to the system's internal energy, which is affected by heat and work.
Which of the following statements is false?
C. A bomb calorimeter measures DeltaH directly.
Which of the following does not have a standard enthalpy of formation equal to zero at 25C and 1.0 atm?
C. H2O(l)
Which of the following properties is (are) intensive properties? I. Mass II. Temperature III. Volume IV. Concentration V. Energy
C. II and IV
Calculate DeltaH for the reaction C4H4+2H2=C4H8 using the following data: DeltaH for C4H4= -2341 kJ/mol; DeltaH for H2= -286 kJ/mol; DeltaH for C4H8= -2755 kJ/mol
B. -158 kJ
At 25C, the following heats of reaction are known: 2ClF + O2 = Cl2O + F2O DeltaH1= 167.4 kJ/mol; 2ClF3 + 2O2 = Cl2O + 3F2O DeltaH2= 341.4 kJ/mol; 2F2 + O2 = 2F2O DeltaH3= -43.4 kJ/mol At the same temp, calculate DeltaH for the reaction: ClF + F2 = ClF3
D. -108..7 kJ/mol
Which of the following statements is/are true? I. q (heat) is a state function because DeltaH is a state function and q=DeltaH II. When 50.0g of aluminum at 20C is placed in 50 mL of water at 30C, the H2O will undergo a smaller temperature change than the aluminum. (The density of H2O=1.0 g/mL, specific heat capacity of H2O=4.18 J/g*C, specific heat capacity of aluminum= 0.89 J/g*C III. When a gas is compressed, the work is negative since the surroundings are doing work on the system and energy flows out of the system. IV. For the reaction (at constant pressure) 2N2(g) + 5O2(g) = 2N2O5(g), the change in enthalpy is the same whether the reaction takes place in one step or in a series of steps
D. II, IV
For a particular process 1=20kJ and w-15kJ. Which of the following statements is true?
DeltaE=35kJ
A bomb calorimeter has a heat capacity of 2.47 kJ/K. When a 0.109 g sample of ethylene (C2H4) was burned in this calorimeter, the temperature increased by 2.22K. Calculate the energy of combustion fo rone mole of ethylene.
E. -1.41*10^3 kJ/mol
If 5.0 kJ of energy is added to a 15.5 g sample of water at 10C, the water is
E. still a liquid
Consider a gas in a 1.0 L bulb at STP that is connected via a valve to another bulb that is initially evacuated. Answer the following concerning what occurs when the valve between the two bulbs is opened. What is true about the value of q?
B. It is equal to zero.
Consider a gas in a 1.0 L bulb at STP that is connected via a valve to another bulb that is initially evacuated. Answer the following concerning what occurs when the valve between the two bulbs is opened. What is true about the value of w?
B. It is equal to zero.
On a cold winter day, a steel metal fence post feels colder than a wooden fence post of identical size because
B. The specific heat capacity of steel is lower than the specific heat capacity of wood
For a particular process q=-17 kJ and w=21 kJ. Which of the following statements is false?
B. The system does work on the surroundings.
For the reaction H2O(l) = H2O(g) at 298K and 1.0atm, DeltaH is more positive than DeltaE by 2.5 kJ/mol. This quantity of energy can be considered to be
B. the work done in pushing back the atmosphere
Consider the following processes: 2A = 1/2B+C DeltaH1= 5 kJ/mol; 3/2B + 4C = 2A + C + 3D DeltaH2= -15 kJ/mol; E + 4A = C DeltaH3= 10 kJ/mol Calculate DeltaH for C = E + 3D
C. -10 kJ/mol
Consider the following processes: 3B = 2C + D DeltaH1= -125 kj/mol; 1/2A = B DeltaH2= 150 kJ/mol; E + A = D DeltaH3= 350 Calculate DeltaH for B= E + 2C
C. -175 kJ/mol
When 0.236 mol of a weak base (A-) is reacted with excess HCl, 6.991 kJ of energy is released as heat. What is DeltaH for this reaction per mole of A- consumed?
C. -29.3 kJ
A fuel-air mixture is placed in a cylinder fitted with a piston. The original volume is 0.310-L. When the mixture is ignited, gases are produce and 935 J of energy is released. To what volume will the gases expand against a constant pressure of 635 mmHg, if all the energy released is converted to work to push the piston?
C. 11.4 L
The DeltaH value for the reaction 1/2O2(g) + Hg(l) = HgO(s) is -90.8 kJ. How much heat is release when 66.9 g Hg is reacteddd with oxygen?
C. 30.3. kJ
You take 295.5 g of a solid at 30.0C and let it melt in 425 g of water. The water temp decreases from 95.1C to 30.0C. Calculate the heat of fusion of this solid.
C. 331 J/g
Consider the reaction: C2H5OH(l) + 3O2(g) = 2CO2(g) + 3H2O(l), DeltaH= -1.37*10^3 kJ When a 21.1 g sample of ethyl alcohol (molar mass= 46.07 g/mol) is burned, how much energy is released as heat?
C. 6.26*10^2 kJ
Using the following thermochemical data: 2Cr + 6HF = 2CrF3 + 3H2 DeltaH= -691.4 kJ/mol 2Cr + 6HCl = 2CrCl3 + 3H2 DeltaH= -559.2 kJ/mol calculate DeltaH for the following reaction: CrF3 + 3HCl = CrCl3 + 3Hf
C. 66.1 kJ/mol
In the lab, you mix two solutions (each originally at the same temperature) and the temperature of the resulting solution decreases. Which of the following is true?
C. The chemical reaction is absorbing energy.
Which of the following statements is correct?
C. The system does work on the surroundings when an ideal gas expands against a constant external pressure.
Which of the following statements correctly describes the signs of q and w for the following exothermic process at P= 1 atm and T= 370K?
C. q is negative, w is positive
What is the enthalpy change when 49.4 mL of 0.430 M sulfuric acid reacts with 23.3 mL of 0.309 M potassium hydroxide? H2SO4(aq) + 2KOH(aq) = K2SO4(aq) + 2H2O(l), DeltaH= -111.6 kJ/mol
A. -0.402 kJ
Using the following thermochemical data, calculate DeltaH of Tm2O3. 2TmCl3 + 3H2O = Tm2O3 + 6HCl DeltaH= 388.1 kJ/mol 2Tm + 3Cl2 = 2TmCl3 DeltaH= -1973.2 kJ/mol 4HCl + O2 = 2Cl2 + 2H2O DeltaH+ -202.4 kJ/mol
A. -1888.7 kJ/mol
A 140.0 g sample of water at 25C is mixed with 11.7 g of a certain metal at 100.0C. After thermal equilibrium is established, the (final) temperature of the mixture is 29.6C. What is the specific heat capacity of the metal, assuming it is constant over the temperature range concerned?
A. 0.34 J/g*C
A 32.5 g piece of aluminum (which has a molar heat capacity of 24.03 J/degrees C*mol) is heated to 82.4 degrees C and dropped into a calorimeter coontaining water (c=4.18) initially at 22.3 degrees C. The final temeperaturee is 24.2C. Ignore sig figs and calculate the mass.
A. 212 g
CH4(g) + 4Cl2(g) = CCl4(g) + 4HCl(g), DeltaH= -434 kJ Based on the above reaction, what energy change occurs when 1.2 moles of methane reacts?
A. 5.2*10^6 J are released
What is the kinetic energy of a 1.56 kg object moving at 94.0 km/hr?
A. 5.32*10^2 kJ
Given the equation S(s) + O2(g) = SO2(g), DeltaH=-296 kJ, which of the following statements are true? I. The reaction is exothermic. II. When 0.500 mole sulfur is reacted, 148 kJ of energy is released. III. When 32g of sulfur are burned, 2.96*10^5 J of energy is released.
A. All are true
C2H5OH(l) + 3O2(g) = 2CO2(g) + 3H2O(l), DeltaH= -1.37*10^3 kJ For the combustion of ethyl alcohol as described in the above equation, which of the following is true? I. The reaction is exothermic. II. The enthalpy change would be different if gaseous water was produced. III. The reaction is not an oxidation-reduction one. IV. The products of the reaction occupy a larger volume than the reactants.
A. I, II
Two metals of equal mass with different heat capacities are subjected to the same amount of heat. Which undergoes the smallest change in temperature?
A. The metal with the higher heat capacity
The heat of formation of Fe2O3 is -826.0 kJ/mol. Calculate the heat of the reaction 4Fe + 3O2 = 2Fe2O3 when a 53.99 g sample of iron is reacted
B. -399.2 kJ
Calculate the work associated with the expansion of a gas from 42.0 L to 79.0 L at a constant pressure of 14.0 atm.
B. -518 L*atm
Given the heats of the following reactions: I. P4(s) + 6Cl2 = 3PCl3, DeltaH= -1225.6 kJ/mol II. P4 + 5O3 = P4O10, DeltaH=-2967.3 kJ/mol III. PCl3 + Cl2 = PCl5, DeltaH= -84.2 kJ/mol IV. PC;3 + 1/2O2 = Cl3PO, DeltaH= -285.7 kJ/mol Calculate the value of DeltaH for the reaction below: P4O10 + 6PCl5 = 10Cl3PO
B. -610.1 kJ
What is the specific heat capacity of silver if it requires 86.3 J to raise the temp of 15 g of silver by 25C?
B. 0.23 J/g*C
Exactly 123.7 J will raise the temperature of 10.0g of a metal from 25C to 60C. What is the specific heat capacity of the metal?
B. 0.353 J/g*C
30.0mL of pure water at 282K is mixed with 50.0mL of pure water at 306K. What is the final temperature of the mixture?
B. 297 K
The heat of combustion of benzene, C6H6, is -41.74 kJ/g. Combustion of 2.82 g of benzene causes a temp rise of 3.29C in a certain bomb calorimeter. What is the heat capacity of this bomb calorimeter?
B. 35.8 kJ/C
Calculate the work associated with the compression of a gas from 121.0L to 80.0L at a constant pressure of 13.1 arm.
B. 537 atm
The enthalpy of fusion of ice is 6.020 kJ/mol. The heat capacity of liquid water is 75.4 J/mol*C. What is the smallest number of ice cubes at 0C, each containing one mole of water, necessary to cool 500 g of liquid water from 20C to 0C?
B. 7
One mole of an ideal gas is expanded from a volume of 1.00 liter to a volume of 8.93 liters against a constant external pressure of 1.00 atm. How much work (in Joules) is performed on the surroundings? Ignore sig figs. (T= 300K; 1 L*atm= 101.3 J)
B. 803 J
A 45.9g sample of a metal is heated to 95.2C and then placed in a calorimeter containing 120.0g of water (c=4.18 J/g*C) at 21.6C. The final temperature of the water is 24.5C. Which metal was used?
B. Iron (c=0.45 J/g*c)
Consider a gas in a 1.0 L bulb at STP that is connected via a valve to another bulb that is initially evacuated. Answer the following concerning what occurs when the valve between the two bulbs is opened. What is true about the value of DeltaE?
B. It is equal to zero.
Consider a gas in a 1.0 L bulb at STP that is connected via a valve to another bulb that is initially evacuated. Answer the following concerning what occurs when the valve between the two bulbs is opened. What is true about the value of DeltaH?
B. It is equal to zero.
Calculate the work for the expansion of CO2 from 1.0 to 4.7 liter against a pressure of 1.0 atm at constant temperature.
D. -3.7 L*atm
A gas absorbs 0.0 J of heat and then performs 30.7 J of work. The change in internal energy of the gas is
D. -30.7 J
What is the specific heat capacity of a metal if it requires 178.1 J to change the temperature of 15.0 g of the metal from 25C to 32C?
D. 1.70 J/g*C
How much heat is liberated at constant pressure when 2.35 g of potassium metal reacts with 5.68 mL of liquid iodine monochloride (d=3.24 g/mL)? 2K(s) + ICl(l) = KCl(s)+KI(s), DeltaH= -740.71 kJ/mol
D. 2.23*10^1 kJ
The total volume of hydrogen gas needed to fill the Hindenburg was 2.11*10^8 L at 1.00 atm and 24.7C. How much energy was evolved when it burned? H2(g)+1/2O2(g) = H2O(l), DeltaH= -286kJ
D. 2.47*10^9 kJ
A chunk of lead at 91.6C was added to 200.0g of water at 15.5C. The specific heat of lead is 0.129 J/g*C and the specific heat of water is 4.18. When the temp stabilized, the temperature of the mixture was 17.9C. What was the mass of lead added?
D. 211 g
A 4.4 g sample of Colorado oil shale is burned in a bomb calorimeter, which causes the temperature of the calorimeter to increase by 5C. The calorimeter contains 1.00 kg of water (c=4.184) and the heat capacity of the empty calorimeter is 0.10 kJ/C. How much heat is released per gram of oil shale when it is burned?
D. 4.9 kJ/g
Consider the following numbered processes: 1. A = 2B 2. B = C+D 3. E = 2D; DeltaH for the process A = 2C + E is
D. DeltaH1 + 2DeltaH2 - DeltaH3
If a student performs an endothermic reaction in a calorimeter, how does the calculated value of DeltaH from the actual value if the heat exchanged with the calorimeter is not taken into account?
D. DeltaHcalc would be less positive because the reaction absorbs heat from the calorimeter
How much heat is required to raise the temerpature of a 5.75 g sample of iron (specific heat = 0.450 J/g*degrees C) from 25 to 79.8 degrees C?
E. 142 J
Consider the reaction H2(g) + 1/2O2(g) = H2O(l) DeltaH= -286 kJ Which of the following is true?
E. Both A and C are true
Consider the reaction: C2H5OH(l) + 3O2(g) = 2CO2(g) + 3H2O(l), DeltaH= -1.37*10^3 kJ Consider the following propositions: I. The reaction is endothermic. II. The reaction is exothermic. III. The enthalpy term would be different is the water formed was gaseous. Which of these are true?
E. II, III
Consider the following specific heats of metals (list) If the same amount of heat is added to 25g of each of the metals, which are all at the same initial temp, which metal will have the highest temp?
E. Lead
Which statement is true of a process in which one mole of gas is expanded from state A to state B?
E. The amount of heat released in the process will depend on the path taken.
