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Internal Energy

Q. When 0.100 g of graphite is burned completely in a bomb calorimeter (heat capacity = 3.344 kJ/°C, containing 3000 g of water, a temperature rise of 0.21°C is observed. What is ΔE for the combustion of graphite? The specific heat of liquid water is 4.184 J/g•°C. 1. ΔE = -40.1 kJ/mol 2. ΔE = -3.34 kJ/mol 3. ΔE = +3.34 kJ/mol 4. ΔE = -285 kJ/mol 5. ΔE = -401.0 kJ/mol

Solved • Apr 22, 2020

Internal Energy

Q. A 1.00 g sample of n-hexane (C6H14) undergoes complete combustion with excess o2 in a bomb calorimeter. The temperature of the 1502 g of water surrounding the bomb rises from 22.64°C to 29.30°C. The heat capacity of the hardware component of the calorimeter (everything that is not water) is is 4042 J/°C. What is ΔU for the combustion of n-C6H14? One mole of n-C6H14 is 86.1 g. The specific heat of water is 4.184 J/g•°C. 1. -9.96 x 10^3 kJ/mol 2. -1.15 x 10^4 kJ/mol 3. -5.92 x 10^3 kJ/mol 4. -4.52 x 10^3 kJ/mol 5. -7.40 x 10^4 kJ/mol

Solved • Apr 22, 2020

Internal Energy

Q. The standard molar heat of fusion of ice is 6020 J/mol. Calculate q, w, and ΔE for melting 1.00 mol ice at 0°C and 1.00 atm pressure. 1. q = 6020 J/mol, w = -6020 J/mol, and ΔE = 0 2. q = 6020 J/mol, w = 6020 J/mol, and ΔE = 12040 J/mol 3. q = 6020 J/mol, w = 0, and ΔE = 6020 J/mol 4. q = -6020 J/mol, w = 0, and ΔE = -6020 J/mol 5. q = -6020 J/mol, w = 6020 J/mol, and ΔE = 0

Solved • Apr 22, 2020

Internal Energy

Q. Assuming the gases are ideal, consider the work done on the system in each of the following reactions: a) The conversion of one mole of brown nitrogen dioxide into colorless dinitrogen tetroxide at 30.0°C: 2NO(g) → N2O4(g) b) The decomposition of one mole of an air pollutant, nitric oxide, at 300°C: 2NO2(g) → N2(g) + O2(g) Calculate the work done on (a) followed by the work done on (b). 1. -1.26 kJ; 0 2. +25.3 kJ; 0 3. +1.26 kJ; 0 4. -1.26 kJ; -1.26 kJ

Solved • Apr 22, 2020

Internal Energy

Q. An ideal gas is allowed to expand isothermally from 2.00 L at 5.00 atm in two steps; a) against a constant external pressure of 3.00 atm, followed by b) against a constant external pressure of 2.00 atm. Calculate q and w. (1.1.33 J = 1 L atm) 1. q = 743 J; w = -743 J. 2. q = 0 J; w = 0 J. 3. q = 125 J; w = -916 J. 4. q = 743 kJ; w = -743 kJ.

Solved • Apr 22, 2020

Internal Energy

Q. The combustion of sucrose (a carbohydrate) is shown as follows C12H22O11(s) + 12O2(g) → 12 CO2(g) + 11H2O(ℓ) Calculate the work, ΔH°at 298 K, and ΔE° for the combustion of one mole of sucrose at 25°C and pressure. ΔHfsucrose = -2218 kJ/mol.

Solved • Apr 22, 2020

Internal Energy

Q. The standard molar internal energy of formation of N2O5(g) is 17.433 kJ/mol at 298 K. What is the standard molar enthalpy of formation of N2O5(g) at the same temperature? 1. 11.24 kJ/mol 2. None of the other answers is correct within 2% 3. 7.921 kJ/mol 4. 19.07 kJ/mol 5. 4.955 kJ/mol

Solved • Apr 22, 2020