CHEM 11H Lecture Notes - Lecture 10: Calorimetry, Joule, Enthalpy

• School: Santa Clara University
• Department: Chemistry and Biochemistry
• Course: CHEM 11H
• Professor: Tan

Document Summary

Recall that e = q + w and w = -pv. If v = 0 (constant volume), e = qv. Enthalpy is a state function h the same whether reaction is in 1 step or in a series of steps. Ex: n2 (g) + 2 o2 (g) 2 no2 (g) N2 (g) + o2 (g) 2 no (g) 2 no (g) + o2 (g) 2 no2 (g) Net: n2 (g) + 2 o2 (g) 2 no2 (g) If reaction is reversed, sign of h is also reversed. Magnitude of h is proportional to the quantities of reactants & products. 2x (a + 2b 3c) 2a + 4b 6c h1 * 2. Sometimes reactions are too difficult/dangerous or impossible to obtain h with calorimetry. Can use standard enthalpy of formation, hf to calculate hrxn. Elements (in standard states) compound (1 mol in standard state) h = hf . By definition: hf for pure element at standard state = 0.