Chapter 9 Thermodynamics Answers

Chemistry Study Guide
Oct 2nd 1 hour Exam

Chapter 9- Thermodynamics

KE= ½ mv2

w= F∆x w= force × distance

∙ A state function refers to a property of the system that depends only on its present state.
∙Internal Energy = heat + work
∆E = q + w
∙Pressure = Force/Area = P = F/A
∙Work= - external pressure × change in volume w = - P∆V

Enthalpy

H = E + PV qp = ∆E + P∆V
∆H = qp

∆H = H products – H reactants

Ideal Gas Law

PV = nRT
Energy "heat" = 3/2 R∆T
Cv = 3/2 R = "heat" required to change the temp of 1 mol of gas by 1K at constant volume Energy required = "heat" – energy needed - energy needed to do to change the translational the
∙ As n increases, the size of the orbital increases, and the electron is easier to remove.

∙ Exceptions :
Be to B – decrease in IE shows that the electrons in 2s orbital effectively shield the 2p electron.

N to O- drop in IE because of addition of electron in first p orbital that results in a pair that repel each other and make either of them easier to remove.

Electron Affinity

X(g) + e-→ X- (g)

∙ Down a group – more positive since electron is added at increasing distances from the nucleus.

∙ Increase across period because effective nuclear charge is increasing.

Electronegativity = (Electron Affinity + Ionization Potential)/2

Lattice Energy

Li+ (g)+ Cl- (g) → LiCl(s)
Lattice Energy = k(Q1Q2)/r

∆H = ∑ D(Bonds broken) - ∑D(Bonds