Question

6-8 Using the table below, calculate the AH rxn for each of the following equations. Selected Standard Enthalpies of Formation at 25° C (298K) AH (kJ/mol) (kJ/mol Formula AH 0 Silver 92.3 Agis) AgC(3) 0 1270 218 Formula AH (kJ/mol Formula Calcium Ca(s) CI (9) Ca(s) 635.1 HC (G) Caco (s)-1206.9 Hydrogen Hig) Carbon C(graphite) 0 H (9) C(diamond) 1.9 Nitrogen COL) -1105 N19) CO(g) -393.5 NH,(g CH_(9) 74.9 NO(9) CH,OHI) -238.6 Oxygen HỎNG) 133 O.) CS.) 87.9 O (9) Chlorine H2O(g) CI(9) 121.0 HO() 0 -45.9 903 Sodium Na(s) 0 Nalg) 1078 Nacks) 411.1 Sulfur S.(rhombic) 0 Symonoclinic)0.3 SO_19) 296.8 SO (9) 396.0 0 143 -241.8 -285.8 H2S = -20.2 CCl4 = -139 a. 2 H2S (g) + 3 O2(g) - 2 SO2(g) + 2 H20 g) b. CH4 (9) + Cl2 (g) - CCL (g) + HCI (g) {Unbalanced] 6-9 Three of the reactions that occur when the paraffin of a candle (typical formula Cz1H(s) burns are: 1. Complete combustion forms CO2 and water vapor 2. Incomplete combustion forms CO and water vapor 3. Some Wax is oxidized to elemental carbon (soot) and water vapor a. Find the AHan for each reaction (AH. of C21H44(S) = -476 kJ/mole) Use graphite for elemental carbon. Use the table in problem 6.9 for other enthalpies of formation.

Answer 1

∆H_rxn= (of enthalpy of formation of products- enthalpy of formation of reactants)

oll AHR= { THE Producto e off (Reactants 2+125g) + 30,183 —>2507 693 + 2H60,9) SHf = - 20.2 kJ/mole, SH60) = 0 Hersos = –2968 kJ/mole, ohin= = -241.8*5 The = (2x04 (302) + 2x SH (20)(2X5Hfst 3X014 (2) OMR = {*4296-81+ 246-241.0)) - [2x420-2)+0] AM(-593.6 – 483-6) - 640.4) AHR = -1077-2 +40.4 FAHR =-1036.8 kJ CHUA , +4212 18) Caluig, + 4H0 (9) shf[Chy) = – 74.9 kJ/mol, AHEA = 0 Off16644) = – 139 ks)ral, Myluch) = - 92.3 kJ/mole Sta= [arfecast 4 x stigumes] - [cHcm+Shf( she = F 139 + 4*692-3)]-[-74.9 +0] ome = [ 139 – 369-2] + 74.9 Pha = - 433.3 kJ |