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109 solutions

Enthalpy of Formation

Q. Given, the following data, calculate the normal boiling point for formic acid (HCOOH). ΔH˚f (kJ/mol) S˚ (J/mol • K) HCOOH (l) –410 130.0 HCOOH (g) –363 250.8

Solved • Dec 3, 2019

Enthalpy of Formation

Q. When 1.50 mol of CH4(g) reacts with excess Cl2(g) at constant pressure according to the chemical equation shown below, 1062 kJ of heat are released. Calculate the value of ΔH (kJ) for this reaction, as written. 2 CH4(g) + 3 Cl2(g) → 2 CHCl3(l) + 3 H2(g) ΔH = ?

Solved • Nov 23, 2019

Enthalpy of Formation

Q. For a particular isomer of C8H18, the combustion reaction produces 5093.7 kJ of heat per mole of C8H18(g) consumed, under standard conditions. C8H18(g) + 25/2 O2(g) → 8 CO2(g) + 9 H2O(g) ΔH°rxn = -5093.7 kJ/mol What is the standard enthalpy of formation of this isomer of C8H18(g)? Standard enthalpy of formation values can be found in this table of thermodynamic values.

Solved • Nov 21, 2019

Enthalpy of Formation

Q. A. Industrial synthesis of urea generally follows the Bosch-Meiser process. A balanced chemical equation for the overall reaction is given below. 2 NH3(l) + CO2(g)→(NH2)2CO(s) + H2O(l) Determine the ΔH° for the above reaction. Is this reaction endothermic or exothermic? B. Determine ΔH° for dissolving urea in water. (NH2)2CO(s) + H2O(l)→(NH2)2CO(aq) Urea must be soluble in water for it to be eliminated by urination. If you dissolve urea in water at room temperature, do you expect the solution to get warmer or colder? Explain your reasoning.

Solved • Nov 20, 2019

Enthalpy of Formation

Q. Which of the following substances have ΔHf° = 0? Select all of the correct answers. a) C(s, graphite) b) F2(g) c) C(s, diamond) d) HCl(g) e) HCl(aq) f) Na(s)

Solved • Nov 19, 2019

Enthalpy of Formation

Q. Calculate the enthalpy change for the following chemical equation. 2SO2(g) + O2(g) → 2SO3(g) Use the following thermochemical data to solve for the change in enthalpy. ΔHf for SO2(g) = -16.9 kJ/mol ΔHf for SO3(g) = -21.9 kJ/mol a) -10.0 kJ/mol rxn b) -77.6 kJ/mol rxn c) +5.0 kJ/mol rxn d) -5.0 kJ/mol rxn

Solved • Nov 19, 2019

Enthalpy of Formation

Q. What mass liquid of ethanol (CH5OH) must be burned to supply 500 kJ of heat? The standard enthalpy of combustion of ethanol at 298 K is -1368 kJ/mol. a) 16.8 g b) 126 g c) 10.9 g d) 29.7 g

Solved • Nov 19, 2019