CHEM 120 Lecture 7: Thermodynamics cntd

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

Document Summary

Energy of chemical reactions: reactants to products. Thermodynamics continued: gauge how much energy is required for a reaction to occur. In precipitation, acid-base, and redox reactions, p v is ~0: with gaseous reactants h2(g) + f2(g) 2hf(g, change in volume depends on mole change, but moles do not change here (1 h + 1 f = 2hf: so p v is again ~0, 2h2(g) + o2(g) 2h2o(g, 3 moles to 2 moles, significant volume change, p v=rt n, p v= -2. 5 * 10^3 j, u= qp + w = qv, w=-p v, qp= p v + u, h=qp. Water or ice: water, it is denser than ice. Ice has a crystalline structure, when water is frozen the molecules spread out, with longer, weaker intermolecular bonds than water, making the bonds easier to break, thus the specific heat is lower. James joule (discovery 1850: used device to find it took 4. 2j to raise 1g of water by 1 degree celsius.