University:
Cornell University
Course:
CHEM 2070 | General Chemistry I
Academic year:

2019
Views:

303

Pages:

2
Author:

Moses Higgins

Thermochemistry - Hess’s Law Problems N2(g) + 2 O2(g)  2 NO2(g) N2(g) + 2 O2(g)  N2O4(g) Calculate the H for the dimerization of NO2: 1. Given the following data: 2 NO2(g)  N2O4(g) H = 67.7 kJ H = 9.7 kJ (answer : -58 kJ) C2H2(g) + 2.5 O2(g)  2 CO2(g) + H2O(l) C(s) + O2(g)  CO2(g) H2(g) + ½ O2(g)  H2O(l) 2. Given the following data: calculate H for the reaction 2C(s) + H2(g)  3. Given the following data: C2H2(g) (answer: +226 kJ) (answer: -233 kJ) NO(g) calculate H for the reaction 2 O3(g)  3 O2(g) O2(g)  2 O(g) + O3(g)  NO2(g) + O2(g) H = -427 H = +495 H = -199kJ NO(g) + O(g)  NO2(g) 4. The formation reaction showing how methanol, CH3OH, is as follows: C + 2 H2 + ½ O 2  CH3OH Given: 2 CH3OH +3 O2  2 CO2 + 4 H2O C + O2  CO2 H2(g) + ½ O2  H2O Calculate the H for the formation of methanol. H = -1452 kJ H = - 394 kJ H = -286 kJ H = - 1300 kJ H = -394 kJ H = -286 kJ 5. (a) Calculate the value of H for the reaction: 3 Fe(s) + 4 H2O(g)  Fe3O4(s) + 4 H2(g) using the given information below. FeO(s) + H2(g)  Fe(s) + H2O(g) 3 FeO(s) + ½ O2(g)  Fe3O4(s) H2(g) + ½ O2(g)  H2O(g) H = + 25 kJ H = -318 kJ H = -242 kJ 6. Using the information below calculate the H for the reaction : C2H2  2 C + H2 C + O2  CO2 H = -394 kJ 2 H2 + O2  2 H2O H = - 572 kJ 2 C2H2 + 5 O2  4 CO2 + 2 H2O H = -2600 kJ 7.The bombardier beetle uses an explosive discharge as a defensive measure. The chemical reaction involved is the oxidation of hydroquinone by hydrogen peroxide to produce quinone and water: C6H4(OH)2(aq) + H2O2(aq)  C6H4O2(aq) + 2 H2O(l) Calculate H for this reaction from the following data: (answer : -202.6 kJ) C6H4(OH)2(aq)  H2(g) + O2(g)  H2(g) + ½ O2(g)  H2O(g)  C6H4O2(aq) + H2(g) H2O2(aq) H2O(g) H2O(l) H H H H = +177.4 kJ = -191.2 kJ = -241.8 kJ = - 43.8 kJ