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chemistry a molecular approach
Questions and Answers of
Chemistry A Molecular Approach
The propane fuel (C3H8) used in gas barbeques burns according to the thermochemical equation:If a pork roast must absorb 1.6 * 103 kJ to fully cook, and if only 10% of the heat produced by the
Charcoal is primarily carbon. Determine the mass of CO2 produced by burning enough carbon (in the form of charcoal) to produce 5.00 * 102 kJ of heat. C(s) + O₂(8) CO₂(8) AHxn=-393.5 kJ
A silver block, initially at 58.5 °C, is submerged into 100.0 g of water at 24.8 °C, in an insulated container. The final temperature of the mixture upon reaching thermal equilibrium is 26.2 °C.
A 32.5-g iron rod, initially at 22.7 °C, is submerged into an unknown mass of water at 63.2 °C, in an insulated container.The final temperature of the mixture upon reaching thermal equilibrium is
A 2.74-g sample of a substance suspected of being pure gold is warmed to 72.1 °C and submerged into 15.2 g of water initially at 24.7 °C. The final temperature of the mixture is 26.3 °C. What is
Exactly 1.5 g of a fuel burns under conditions of constant pressure and then again under conditions of constant volume. In measurement A the reaction produces 25.9 kJ of heat, and in measurement B
In order to obtain the largest possible amount of heat from a chemical reaction in which there is a large increase in the number of moles of gas, should you carry out the reaction under conditions of
When 0.514 g of biphenyl (C12H10) undergoes combustion in a bomb calorimeter, the temperature rises from 25.8 °C to 29.4 °C.Find ΔErxn for the combustion of biphenyl in kJ/mol biphenyl.The heat
Zinc metal reacts with hydrochloric acid according to the balanced equation:When 0.103 g of Zn(s) is combined with enough HCl to make 50.0 mL of solution in a coffee-cup calorimeter, all of the zinc
Mothballs are composed primarily of the hydrocarbon naphthalene (C10H8). When 1.025 g of naphthalene burns in a bomb calorimeter, the temperature rises from 24.25 °C to 32.33 °C.Find ΔErxn for the
Instant cold packs used to ice athletic injuries on the field contain ammonium nitrate and water separated by a thin plastic divider. When the divider is broken, the ammonium nitrate dissolves
For each generic reaction, determine the value of ΔH2 in terms of ΔH1. a. A + B -2C 2C — A + B b. A + 12B — C 2 A + B - 2C c. A → B + 2 C 1/2B + C - → • 1/2A ΔΗ, ΔΗ, = ? ΔΗ ΔΗ, =
Consider the generic reaction:Determine the value of ΔH for each related reaction. A + 2B C + 3D → AH = 155 kJ
Calculate ΔHrxn for the reaction:Use the following reactions and given ΔH’s: 5 C(s) + 6 H₂(8) C5H12(1)
Calculate ΔHrxn for the reaction:Use the following reactions and given ΔH’s: Fe₂O3(s) + 3 CO(g) 2 Fe(s) + 3 CO2(8)
Calculate ΔHrxn for the reaction:Use the following reactions and given ΔH’s: CaO(s) + CO2(g) CaCO3(s)
Calculate ΔHrxn for the reaction:Use the following reactions and given ΔH’s: CH4(g) + 4 Cl2(g) CC14(g) + 4 HCl(g)
Write an equation for the formation of each compound from its elements in their standard states, and find ΔH°f for each in Appendix IIB.a. NH3(g) b. CO2(g) c. Fe2O3(s) d. CH4(g)
Use standard enthalpies of formation to calculate ΔH°rxn for each reaction. a. C₂H4(g) + H₂(g) C₂H6(8) b. CO(g) + H₂O(g) →→→ H₂(g) + CO₂(g) c. 3 NO₂(g) + H₂O(1) d. Cr₂O3(s)
Write an equation for the formation of each compound from its elements in their standard states, and find ΔH °rxn for each.a. NO2(g) b. MgCO3(s) c. C2H4(g) d. CH3OH(l)
Use standard enthalpies of formation to calculate ΔH°rxn for each reaction. 2 H₂O(l) +2 SO₂(8) SO3(8) a. 2 H₂S(g) + 3 O₂(g) b. SO2(g) + ¹/2O2(8) c. C(s) + H₂O(g) →→→ CO(g) +
Top fuel dragsters and funny cars burn nitromethane as fuel according to the balanced combustion equation:Calculate the standard enthalpy of formation (ΔH°f) for nitromethane. 2 CH3NO₂(1) +
During photosynthesis, plants use energy from sunlight to form glucose (C6H12O6) and oxygen from carbon dioxide and water. Write a balanced equation for photosynthesis and calculate ΔH°rxn.
Ethanol (C2H5OH) can be made from the fermentation of crops and has been used as a fuel additive to gasoline. Write a balanced equation for the combustion of ethanol and calculate ΔH°rxn.
The explosive nitroglycerin (C3H5N3O9) decomposes rapidly upon ignition or sudden impact according to the balanced equation:Calculate the standard enthalpy of formation (ΔH°f) for nitroglycerin. 4
Determine the mass of CO2 produced by burning enough of each fuel to produce 1.00 * 102 kJ of heat. Which fuel contributes least to global warming per kJ of heat produced? a. CH.(g) + 2 O2(g) b.
Methanol (CH3OH) has been suggested as a fuel to replace gasoline.Write a balanced equation for the combustion of methanol, find ΔH°rxn, and determine the mass of carbon dioxide emitted per kJ of
The citizens of the world burn the fossil fuel equivalent of 7 * 1012 kg of petroleum per year. Assume that all of this petroleum is in the form of octane (C8H18) and calculate how much CO2 (in kg)
In a sunny location, sunlight has a power density of about 1 kW/m2. Photovoltaic solar cells can convert this power into electricity with 15% efficiency. If a typical home uses 385 kWh of electricity
The kinetic energy of a rolling billiard ball is given by KE = 1/2 mv2. Suppose a 0.17-kg billiard ball is rolling down a pool table with an initial speed of 4.5 m/s. As it travels, it loses some of
Evaporating sweat cools the body because evaporation is an endothermic process:Estimate the mass of water that must evaporate from the skin to cool the body by 0.50 °C. Assume a body mass of 95 kg
A 100-W lightbulb is placed in a cylinder equipped with a moveable piston. The lightbulb is turned on for 0.015 hour, and the assembly expands from an initial volume of 0.85 L to a final volume of
LP gas burns according to the exothermic reaction:What mass of LP gas is necessary to heat 1.5 L of water from room temperature (25.0 °C) to boiling (100.0 °C)? Assume that during heating, 15% of
Derive a relationship between ΔH and ΔE for a process in which the temperature of a fixed amount of an ideal gas changes.
Under certain nonstandard conditions, oxidation by O2(g) of 1 mol of SO2(g) to SO3(g) absorbs 89.5 kJ. The enthalpy of formation of SO3(g) is -204.2 kJ under these conditions. Find the enthalpy of
One tablespoon of peanut butter has a mass of 16 g. It is combusted in a calorimeter whose heat capacity is 120.0 kJ/°C. The temperature of the calorimeter rises from 22.2 °C to 25.4 °C.Find the
A mixture of 2.0 mol of H2( g) and 1.0 mol of O2( g) is placed in a sealed evacuated container made of a perfect insulating material at 25 °C. The mixture is ignited with a spark and reacts to form
A 20.0-L volume of an ideal gas in a cylinder with a piston is at a pressure of 3.0 atm. Enough weight is suddenly removed from the piston to lower the external pressure to 1.5 atm. The gas then
When 10.00 g of phosphorus is burned in O2(g) to form P4O10(s), enough heat is generated to raise the temperature of 2950 g of water from 18.0 °C to 38.0 °C. Calculate the enthalpy of formation of
The ΔH for the oxidation of sulfur in the gas phase to SO3 is -204 kJ/mol and for the oxidation of SO2 to SO3 is 89.5 kJ/mol.Find the enthalpy of formation of SO2 under these conditions.
The ΔH°f of TiI3(s) is -328 kJ/mol and the ΔH° for the reaction 2 Ti(s) + 3 I2( g) → 2 TiI3(s) is -839 kJ. Calculate the ΔH of sublimation of I2(s), which is a solid at 25 °C.
A gaseous fuel mixture contains 25.3% methane (CH4), 38.2% ethane (C2H6), and the rest propane (C3H8) by volume. When the fuel mixture contained in a 1.55 L tank, stored at 755 mmHg and 298 K,
A gaseous fuel mixture stored at 745 mmHg and 298 K contains only methane (CH4) and propane (C3H8). When 11.7 L of this fuel mixture is burned, it produces 769 kJ of heat. What is the mole fraction
A copper cube with an edge measuring 1.55 cm and an aluminum cube with an edge measuring 1.62 cm are both heated to 55.0 °C and submerged in 100.0 mL of water at 22.2 °C. What is the final
A pure gold ring and a pure silver ring have a total mass of 14.9 g.The two rings are heated to 62.0 °C and dropped into 15.0 mL of water at 23.5 °C. When equilibrium is reached, the temperature of
A typical frostless refrigerator uses 655 kWh of energy per year in the form of electricity. Suppose that all of this electricity is generated at a power plant that burns coal containing 3.2% sulfur
A large sport utility vehicle has a mass of 2.5 * 103 kg. Calculate the mass of CO2 emitted into the atmosphere upon accelerating the SUV from 0.0 mph to 65.0 mph. Assume that the required energy
Combustion of natural gas (primarily methane) occurs in most household heaters. The heat given off in this reaction is used to raise the temperature of the air in the house. Assuming that all the
The heat of vaporization of water at 373 K is 40.7 kJ/mol. Find q, w, ΔE, and ΔH for the evaporation of 454 g of water at this temperature at 1 atm.
Find ΔE, ΔH, q, and w for the change in state of 1.0 mol H2O(l ) at 80 °C to H2O( g) at 110 °C. The heat capacity of H2O(l) = 75.3 J/mol K, the heat capacity of H2O( g) = 25.0 J/mol K, and the
The heat of combustion of liquid octane (C8H18) to carbon dioxide and liquid water at 298 K is -1303 kJ/mol. Find ΔE for this reaction.
Find ΔH for the combustion of ethanol (C2H6O) to carbon dioxide and liquid water from the following data. The heat capacity of the bomb calorimeter is 34.65 kJ/K, and the combustion of 1.765 g of
Which statement is true of the internal energy of the system and its surroundings following a process in which ΔEsys = +65 kJ ?Explain.a. The system and the surroundings both lose 65 kJ of energy.b.
The internal energy of an ideal gas depends only on its temperature. Which statement is true of an isothermal (constant-temperature) expansion of an ideal gas against a constant external pressure?
Which expression describes the heat evolved in a chemical reaction when the reaction is carried out at constant pressure? Explain.a. ΔE - w b. ΔE c. ΔE - q
Two identical new refrigerators are plugged in for the first time. Refrigerator A is empty (except for air) and refrigerator B is filled with jugs of water. The compressors of both refrigerators
A 1-kg cylinder of aluminum and 1-kg jug of water, both at room temperature, are put into a refrigerator. After 1 hour, the temperature of each object is measured. One of the objects is much cooler
Two substances A and B, initially at different temperatures, are thermally isolated from their surroundings and allowed to come into thermal contact. The mass of substance A is twice the mass of
When 1 mol of a gas burns at constant pressure, it produces 2418 J of heat and does 5 J of work. Determine ΔE, ΔH, q, and w for the process.
Have each group member write a problem involving the transfer of heat from one material in Table 7.4 to another material in the table. Working as a group, solve each problem. The group member who
In an exothermic reaction, the reactants lose energy, and the reaction feels hot to the touch. Explain why the reaction feels hot even though the reactants are losing energy. Where does the energy
Which statement is true of a reaction in which ΔV is positive?Explain.a. ΔH = ΔE b. ΔH > ΔE c. ΔH < ΔE
The heating value of combustible fuels is evaluated based on the quantities known as the higher heating value (HHV) and the lower heating value (LHV). The HHV has a higher absolute value and assumes
Classify each process as endothermic or exothermic. What is the sign of ΔH for each process? Explain your answers.a. Gasoline burning in an engine b. Steam condensing on a mirror c. Water boiling
Calculate the wavelength (in nm) of the red light emitted by a barcode scanner that has a frequency of 4.62 * 1014 s-1.
Which statement best describes the differences between a bright green laser and a dim red laser?(a) The two lasers emit light of the same frequency, and the light from the green laser has a greater
A nitrogen gas laser pulse with a wavelength of 337 nm contains 3.83 mJ of energy. How many photons does it contain? SORT You are given the wavelength and total energy of a light pulse and asked to
Which wavelength of light has the highest frequency?a) 10 nm b) 10 mm c) 1 nm d) 1 mm
Why is the quantum-mechanical model of the atom important for understanding chemistry?
Arrange the following types of electromagnetic radiation in order of increasing wavelength: visible, X-ray, infrared.(a) X-ray 6 visible 6 infrared (b) X-ray 6 infrared 6 visible (c) Visible 6
Which kind of electromagnetic radiation contains the greatest energy per photon?a) Microwaves b) Gamma raysc) X-rays d) Visible light
What is light? How fast does it travel in a vacuum?
We shine light of three different wavelengths—325 nm, 455 nm, and 632 nm—on a metal surface and record the following observations for each wavelength, labeled A, B, and C:Observation A: No
Calculate the wavelength of an electron traveling with a speed of 2.65 * 106 m/s. SORT You are given the speed of an electron and asked to calculate its wavelength. STRATEGIZE The conceptual plan
How much energy (in J) is contained in 1.00 mole of 552-nm photons?a) 3.60 * 10-19 J b) 2.17 * 105 Jc) 3.60 * 10-28 Jd) 5.98 * 10-43 J
Define the wavelength and amplitude of a wave. How are these related to the energy of the wave?
Since quantum-mechanical theory is universal, it applies to all objects, regardless of size. Therefore, according to the de Broglie relation, a thrown baseball should also exhibit wave properties.
Light from three different lasers (A, B, and C), each with a different wavelength, was shined onto the same metal surface.Laser A produced no photoelectrons. Lasers B and C both produced
What are the quantum numbers and names of the orbitals in the n = 4 principal level?How many n = 4 orbitals exist?
Define the frequency of electromagnetic radiation. How is frequency related to wavelength?
Which statement best summarizes the uncertainty principle?(a) Both the position and the velocity of an electron can be accurately known at the same instant.(b) Either the position or the velocity of
Calculate the wavelength of an electron traveling at 1.85 * 107 m/s.a) 2.54 * 1013 m b) 3.93 * 10-14 mc) 2.54 * 1010 m d) 3.93 * 10-11 m
What determines the color of light? Describe the difference between red light and blue light.
These sets of quantum numbers are each supposed to specify an orbital. One set, however, is erroneous. Which one and why?(a) n = 3; l = 0; ml = 0 (b) n = 2; l = 1; ml = -1(c) n = 1; l = 0; ml =
Which set of three quantum numbers does not specify an orbital in the hydrogen atom? a) n = 2; 1= 1; m₁ = − 1 c) n = 2; 1= 0; m₁ = 0 b) n = 3; 1= d) n = 3; 1= 3; m₁ = −2 2; m₁ = 2
What values of l are possible for n = 3?(a) 0 (or s) (b) 0 and 1 (or s and p)(c) 0, 1, and 2 (or s, p, and d) (d) 0, 1, 2, and 3 (or s, p, d, and f)
Determine the wavelength of light emitted when an electron in a hydrogen atom makes a transition from an orbital in n = 6 to an orbital in n = 5. SORT You are given the energy levels of an atomic
What determines the color of a colored object? Explain why grass appears green.
Give an approximate range of wavelengths for each type of electromagnetic radiation and summarize the characteristics and/or the uses of each.a. Gamma rays b. X-raysc. Ultraviolet radiation d.
Which transition emits light with the shortest wavelength? (a) n = 5→→→→→→→n (c) n = 3n = 4 = 2 (b) n=4 → n = 3
Explain the wave behavior known as interference. Explain the difference between constructive and destructive interference.
Which electron transition produces light of the highest frequency in the hydrogen atom? a) 5p - c) 3p 1s 1s b) 4p d) 2p 1s 1s
How much time (in seconds) does it take light in a vacuum to travel 1.00 billion km? a) 3.00 x 10¹7 s c) 3.33 x 10³ s b) 3.33 s d) 3.00 x 1020 s
Explain the wave behavior known as diffraction. Draw the diffraction pattern that occurs when light travels through two slits comparable in size and separation to the light’s wavelength.
Which orbital is a d orbital? a) b) c) d) None of the above
Describe the photoelectric effect. How did experimental observations of this phenomenon differ from the predictions of classical electromagnetic theory?
How did the photoelectric effect lead Einstein to propose that light is quantized?
What is a photon? How is the energy of a photon related to its wavelength? Its frequency?
Describe the Bohr model for the atom. How did the Bohr model account for the emission spectra of atoms?
Explain electron diffraction.
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