CHEM 120 Lecture Notes - Lecture 5: Thermodynamics, System 7, Calorimetry

• School: McGill University
• Department: Chemistry
• Course: CHEM 120
• Professor: Laura Pavelka

Document Summary

Chem 120 lecture 5 thermodynamics & heats of reaction. Calorimeter = device for measuring quantities of heat: bomb calorimeter: usually for combustion reactions. Use conservation of energy principles, system is isolated, no energy nor matter is exchanged. C = heat capacity of the entire calorimeter (calibrated & found experimentally: coffee cup calorimeter: simple, well insulated, therefore isolated, measure deltat. In addition to heat effects, chemical reactions may also do work (pressure-volume work) = gas formed pushes against atmosphere, thus volume changes to keep same pressure. W = f*d fatm = patma w = fatmd = patmad w = patm(deltav) 1. a gas is 0. 100 mol he at 298k and each mass corresponds to an external pressure of 1. 20atm. V2 = nrt/p2 = p1/p2 *v1 = 2v1 = 2. 04l deltav = v2 v1 = 1. 02l. W = -pext*(deltav) = -1. 2atm*1. 02l - because pressure against which gas expands.