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 and ideal gas behavior 6 4 Enthalpy of Chemical Reaction 6 24 Consider this reaction What is the value of H 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 Calorimetry 6 5 6 32 A piece of silver of mass 362 g has a heat capacity of 85 7 J C What is the specific heat of silver 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 was found 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 released per gram of the compound reacted with oxygen The standard enthalpy of formation of B5H9 is 73 2 kJ mol Calculate the kilojoules of heat 6 62 Calculate 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 Heats of Solution and Dilution 6 7 6 74 calculate the H rxn for the reaction 6 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 the water decreased from 21 6 C to 18 1 C Calculate the heat of solution Hsoln 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 Quantum theory 7 1 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 45 109 Hz 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 electromagnetic spectrum would you assign it c What is the energy in joules of one quantum of this radiation Bohr s model 7 3 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 Particle Wave Duality 7 4 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 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 …
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