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Hess's Law

Q. Lead can be prepared from galena [lead(II) sulfide] by first heating with oxygen to form lead(II) oxide and sulfur dioxide. Heating the metal oxide with more galena forms the metal and more sulfur dioxide. A. 2PbS + O2 => 2Pb + SO2 B. 2PbS + 2O2 => 2Pb + SO2 C. PbS + 2O2 => 2Pb + SO2 D. 2PbS + O2 => 2Pb + 2SO2 E. PbS + O2 => 2Pb + SO2

Solved • Mar 3, 2020

Hess's Law

Q. Consider these reactions, where M represents a generic metal. 1. 2M(s) + 6HCl(aq) → 2MCl3(aq) + 3H2(g) ΔH1 = -755.0 kJ 2. HCl(g) → HCl(aq) ΔH2 = -74.8 kJ 3. H2(g) + Cl2(g) → 2HCl(g) ΔH3 = -1845.0 kJ 4. MCl3(s) → MCl3(aq) ΔH4 =-236.0 kJ Use the given information to determine the enthalpy of the reaction 2M(s) + 3Cl2(g) →2 MCl3(s)

Solved • Mar 2, 2020

Hess's Law

Q. Given that H2(g) + F2(g) → 2HF(g) ΔH°rxn = -546.6 kJ 2H2(g) + O2(g) → 2H2O(l) ΔH°rxn = -571.6 kJ calculate the value ΔH°rxn for 2F2(g) + 2H2O(l) → 4HF(g) + O2(g)

Solved • Mar 2, 2020

Hess's Law

Q. Calculate the heat of formation of ethanol given that the heat of combustion of liquid ethanol is -326.7kcalmol^-1 while the enthalpy of formation of carbon dioxide and water are -97 and -68kcalmol^-1 respectively. Please show the workings

Solved • Jan 29, 2020

Hess's Law

Q. Using Hess's Law and some or all of the equations (1) - (4) below calculate ΔH° at 25°C for coal gasification:

Solved • Dec 31, 2019

Hess's Law

Q. Using Hess's Law and some or all of the equations (1) - (4) below calculate ΔH° at 25°C for the reaction: NO2(g) + N2O(g) → 3 NO(g). 1. N2(s) + NO2(g) → NO(g) + NO2(g) ΔH1 = +138.1 kJ/mol 2. 2 NO(g) + O2(g) → 2 NO2(g) ΔH2 = –113.1 kJ/mol 3. 2 N2O(g) → O2(g) + 2 N2(g) ΔH3 = –163.2 kJ/mol 4. 2 NO(g) → O2(g) + N2(g) ΔH4 = –180.7 kJ/mol

Solved • Dec 27, 2019

Hess's Law

Q. Use molar enthalpies for reactions 1, 2 and 4-8 (repeated below) CH4 (g) + H2O (g) → 3H2 (g) + CO (g) (rxn 1) CO (g) + H2O (g) → H2 (g) + CO2 (g) (rxn 2) C5H12 (l) + 8O2 (g) → 5CO2 (g) + 6H2O (l) (rxn 4) CH4 (g) + 2O2 → CO2 (g) + 2H2O (l) (rxn 5) CH4 (g) + 3/2O2 → CO (g) + 2H2O (l) (rxn 6) CO (g) + 1/2 O2 (g) → CO2 (g) (rxn 7) H2O (l) → H2O (g) (rxn 8) To determine ΔH° for reaction 3: 11H2 (g) + 5CO → C5H12 (l) + 5H2O (l) (rxn 3) There are several ways to do this with the reactions provided here, you will not need to use all of the chemical equations. Solve algebraically for now; you will be given the H values in recitation.

Solved • Dec 4, 2019