CHEMISTRY 161 Revision Chapters 4-6 chem.hawaii/Bil301/welcome.html

1. CHEMISTRY 161 Revision Chapters 4-6 www.chem.hawaii.edu/Bil301/welcome.html

2. 4. CHEMICAL REACTIONS 4.1. properties of solutions 4.2. reactions in solutions a) precipitation reactions b) acid-base reactions (proton transfer) c) redox reactions (electron transfer)

3. non-electrolyte weak electrolyte strong electrolyte ionic compounds NaOH HCl H2SO4 methanol sugar ethanol water CH3COOH HCOOH HF dark medium bright

4. DISSOCIATION ‘breaking apart’ NaCl (s) → Na+ (aq) + Cl- (aq) NaOH (s) → Na+ (aq) + OH- (aq) HCl (g) → H+ (aq) + Cl- (aq) strong electrolytes are fully dissociated

5. strong electrolyte HCl(aq) + H2O(l) → H3O+(aq) + Cl-(aq) HNO3(aq) + H2O(l) → H3O+(aq) + NO3-(aq) weak electrolyte CH3COOH(aq) + H2O(l) H3O+(aq) + CH3COO-(aq) NH3(aq) + H2O(l) NH4+ + OH- monoprotic acids

6. 4.2.1. insoluble compounds • M+ compounds (M = H, Li, Na, K, Rb, Cs, NH4) • 2. A- compounds (A = NO3, HCO3, ClO3, Cl, Br, I) • (AgX, PbX2) • 3. SO42- • (Ag, Ca, Sr, Ba, Hg, Pb) • 4. CO32-, PO43-, CrO42-, S2- • (exception: M+)

7. 4.2.2. ACID-BASE REACTION acid + base→ salt + water (neutralization reaction) HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l) molecular equation – ionic equation – spectator ions

8. 4.2.3. OXIDATION NUMBER ionic compounds ↔ molecular compounds NaCl HF, H2 ? Na+Cl- covalent bond electrons are fully transferred ‘oxidation number’ charges an atom would have if electrons are transferred completely

9. TYPES OF REDOX REACTIONS • combination reactions • A + B → C 2. decomposition reactions C → A + B 3. displacement reactions A + BC → AC + B 4. disproportionation reactions

10. 5. GASES SI units [p] = Nm-2 = kg m-1 s-2 = Pa

11. 1. ideal gas equation p × V = n × R × T R = 8.314 J / mol / K 2. molar volume Vm = 22.4 l

12. 3. Kinetic Molecular Theory of Gases 4.Distribution of Molecular Speeds Ekin = ½ M u2 = 3/2 R T 5. Real Gas Law (p + (a n2 / V2) ) (V – n b) = n R T

13. 6. THERMOCHEMISTRY Enthalpy of Reaction heat released or absorbed by the system at a constant pressure DH = Hproducts - Hreactants Hfinal > Hinitial : DH > 0 ENDOTHERMIC Hfinal < Hinitial : DH < 0 EXOTHERMIC

14. measurement of heat changes DHm = ΔQm = cmpΔT DH = ΔQ = (cmp × n + ccup) ΔT cmp(H2O) = 75.3 J mol-1 K-1

15. Standard Enthalpy of Formation DHfO heat change when 1 mole of a compound is formed from its elements at a pressure of 1 atm (T = 298 K) DHfO (element) = 0 kJ/mol DHfO (graphite) = 0 kJ/mol DHfO (diamond) = 1.9 kJ/mol

16. C(s, graphite) + O2(g) Hreactants 0 ENTHALPY, H DHf0 = - 393.51 kJ mol-1 Hproducts -393.51 CO2(g)

17. Standard Enthalpy of Formation C(s, graphite) + O2(g) CO2(g) DHf0 = - 393.51 kJ mol-1 CH4(g) DHf0 = - 74.81 kJ mol-1 C(s, graphite) + 2H2(g) DHf0 = - 46.11 kJ mol-1 ½ N2(g) + 3/2 H2(g) NH3(g) NO(g) DHf0 = + 33.18 kJ mol-1 (1/2) N2(g) + (1/2) O2(g)

18. Standard Enthalpy of Reaction DHOrxn = ΣnΔHf0(prod) – ΣmΔHf0(react) CaO(s) + CO2(g) → CaCO3(s) [kJ/mol] -393.5 -1206.9 -635.6 DHOrxn = -177.8 kJ/mol

19. 1 atm = 760 mm Hg = 760 torr = 103,325 Pa R = 8.314 J / mol / K cmp(H2O) = 75.3 J / mol / K p V = n R T Ekin = ½ M u2 = 3/2 R T ΔQ = (cmp × n + ccup) ΔT DHOrxn = ΣnΔHf0(prod) – ΣmΔHf0(react)

20. Come in Time! Do not forget your calculator!