What is the density of lead (in \(g/\mathrm{cm}^{3}\)) if a rectangular bar measuring 0.500 cm in height, 1.55 cm in width, and 25.00 cm in length has a mass of 220.9 g?
Text Transcription:
g/cm^3
Thermochemistry Thermodynamics: the study of the relationships between heat, energy, and work and the conversion of one into the other. System: the substance being evaluated for energy content in a thermodynamic process Surroundings: everything outside the system in a thermodynamic process Change in Internal Energy: the sum of the energy in the form of heat exchanged between system and surroundings and the work done by or on the system; ∆E system q+ w o Q = energy in the form of heat exchanged between system and surroundings o W = work done by or on the system Sign Conventions in Thermodynamics: 1. If q or w is positive, then energy is added to the system and the internal energy of the system increases. 2. If q or w is negative, then energy is removed from the system and the internal energy of the system decreases. Example: Calculate internal energy change A gas expands and does 115 J of work on the surroundings. At the same time, the gas absorbs 230 J of heat from the surroundings. What is the change in the internal energy of the gas ∆E = q + w Q = 230 J W = -115 J ∆ = 230 + -115 = 115 J Enthalpy: the sum of the internal energy of the system and the product of its pressure and volume. Change in Enthalpy (∆H): the energy as heat transferred at constant pressure; direction of energy transfer o Exothermic Process: a thermodynamic process in which energy as heat flows from a system to its surroundings; ∆H < 0
