6.1 – 6.3 Types of Energy Energy Changes in Chemical Reactions Introduction to Thermodynamics 6.14 Consider these changes.1. Hg(l) -> Hg (g)2. 3O2(g)->2O3 (g)3. CuSO4 * 5H2O(s)-> CuSO4(s) + 5H2O(g)4. H2(g)+F2(g)->2HF(g)At constant pressure, in which of the reactions is work done by the system on the surroundings? By the surroundings on the system? In which of them is no work done?6.16 A gas expands in volume from 26.7 mL to 89.3 mL at constant temperature. Calculate the work done (in joules) if the gas expands (a) against a vacuum, (b) against a constant pressure of 1.5 atm, and (c) against a constant pressure of 2.8 atm.6.18 The work done to compress a gas is 74 J. As a result, 26 J of heat is given off to the surroundings. Calculate the change in energy of the gas.6.20 Calculate the work done in joules when 1.0 mole of water vaporizes at 1.0 atm and 100°C. Assume that the volume of liquid water is negligible compared with that of steam at 100°C, andideal gas behavior. 6.4 Enthalpy of Chemical Reaction 6.24 Consider this reaction:What is the value of ΔH if (a) the equation is multiplied throughout by 2, (b) the direction of the reaction is reversed so that the products become the reactants and vice versa, (c) water vapor instead of liquid water is formed as the product?6.26 Determine the amount of heat (in kJ) given off when 1.26 × 104 g of NO2 are produced according to the equation 6.5 Calorimetry6.32 A piece of silver of mass 362 g has a heat capacity of 85.7 J/°C. What is the specific heat ofsilver?6.34 Calculate the amount of heat liberated (in kJ) from 366 g of mercury when it cools from 77.0°C to 12.0°C. 6.36 To a sample of water at 23.4°C in a constant-pressure calorimeter of negligible heat capacity is added a 12.1-g piece of aluminum whose temperature is 81.7°C. If the final temperature of water is 24.9°C, calculate the mass of the water in the calorimeter. 6.38 A quantity of 85.0 mL of 0.900 M HCl is mixed with 85.0 mL of 0.900 M KOH in a constant-pressure calorimeter that has a heat capacity of 325 J/°C. If the initial temperatures of both solutions are the same at 18.24°C, what is the final temperature of the mixed solution? The heat of neutralization is −56.2 kJ/mol. Assume the density and specific heat of the solutions are the same as those for water. 6.88 A 44.0-g sample of an unknown metal at 99.0°C was placed in a constant-pressure calorimeter containing 80.0 g of water at 24.0°C. The final temperature of the system wasfound to be 28.4°C. Calculate the specific heat of the metal. (The heat capacity of the calorimeter is 12.4 J/°C.)6.6 Standard Enthalpy of Formation and Reaction 6.54 Calculate the heats of combustion for the following reactions from the standard enthalpies of formation listed in Appendix 3: 6.56 The standard enthalpy change for the following reaction is 436.4 kJ/mol:Calculate the standard enthalpy of formation of atomic hydrogen (H).6.58 Calculate the kilojoules of heat released per gram of the compound reacted with oxygen. The standard enthalpy of formation of B5H9 is 73.2 kJ/mol.6.62Calculate the enthalpy of formation of methanol (CH3OH) from its elements: 6.100 A quantity of 0.020 mole of a gas initially at 0.050 L and 20°C undergoes a constant-temperature expansion until its volume is 0.50 L. Calculate the work done (in joules) by the gas if it expands (a) against a vacuum and (b) against a constant pressure of 0.20 atm. (c) If the gas in (b) is allowed to expand unchecked until its pressure is equal to the external pressure, what would its final volume be before it stopped expanding, and what would be the work done?6.7 Heats of Solution and Dilution 6.74 calculate the ΔH°rxn for the reaction6.78 A 3.53-g sample of ammonium nitrate (NH4NO3) was added to 80.0 mL of water in a constant-pressure calorimeter of negligible heat capacity. As a result, the temperature of thewater decreased from 21.6°C to 18.1°C. Calculate the heat of solution (ΔHsoln) of ammonium nitrate.6.80 Calculate the heat released when 2.00 L of Cl2(g) with a density of 1.88 g/L react with an excess of sodium metal at 25°C and 1 atm to form sodium chloride.7.1 Quantum theory 7.8 What is the frequency of light having a wavelength of 456 nm? (b) What is the wavelength (in nanometers) of radiation having a frequency of 2.45 × 109Hz? (This is the type of radiation used in microwave ovens.)7.2 The Photoelectric Effect 7.16 The blue color of the sky results from the scattering of sunlight by air molecules. The blue light has a frequency of about 7.5 × 1014 Hz. (a) Calculate the wavelength, in nm, associated with this radiation, and (b) calculate the energy, in joules, of a single photon associated with this frequency.7.20 A particular form of electromagnetic radiation has a frequency of 8.11 × 1014 Hz. (a) What is its wavelength in nanometers? In meters? (b) To what region of the electromagneticspectrum would you assign it? (c) What is the energy (in joules) of one quantum of this radiation?7.3 Bohr’s model 7.30 The first line of the Balmer series occurs at a wavelength of 656.3 nm. What is the energy difference between the two energy levels involved in the emission that results in this spectral line?7.32 Calculate the frequency (Hz) and wavelength (nm) of the emitted photon when an electron drops from the n = 4 to the n = 2 level in a hydrogen atom.7.4 Particle Wave Duality 7.40 Protons can be accelerated to speeds near that of light in particle accelerators. Estimate the wavelength (in nm) of such a proton moving at 2.90 × 108 m/s. (Mass of a proton = 1.673 × 10−27 kg.)7.6-7.7 Quantum Numbers and Atomic Orbitals 7.56 An electron in an atom is in the n = 3 quantum level. List the possible values of ℓ and that it can have.7.58 Give the values of the four quantum numbers of an electron in the following orbitals: (a) 3s, (b) 4p, (c) 3d.7.60 What is the difference between a 2px and a 2py orbital?7.62 List all the possible subshells and orbitals associated with the principal quantum number n,if n = 6.7.64 What is the total number of electrons that can be held in all orbitals having the same principal quantum number n?7.66Indicate the total number of (a) p electrons in N (Z = 7); (b) s electrons in Si (Z = 14); and (c)3delectrons in S (Z = 16).7.68 Why do the 3s, 3p, and 3d orbitals have the same energy in a hydrogen atom but
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