CH2-0-NO2 Question 49 Figure 1 Nitroglycerin It undergoes decomposition violentl
ID: 1042855 • Letter: C
Question
CH2-0-NO2 Question 49 Figure 1 Nitroglycerin It undergoes decomposition violently (Reaction 1) when heated or shocked XBased on the passage, the magnitude of AHo (in kJ) for the O decomposition of 2 moles of nitroglycerin at 25°C is closest to which of Solution the following? 4C3H5N30() 12Co2(g) +10H20(g) 6N2(g) O2(9) Foundational Concept: 5 The principles that govern chemical interactions and reactions form the basis for a broader understanding of the molecular dynamics of living systems Reaction 1 The standard enthalpies of formation at 25°C of the species in Reaction 1 are listed in Table 1 Content Category: 5E Principles of chemical thermodynamics and kinetics Table 1 Standard Enthalpies of Formation at 25°C SpeciesAH°f (kJ/mol) Scientific Inquiry and Reasoning Skill: 4 Data-based and Statistical Reasoning CO2(9) H20(g) N2(9) O2(9) C3HsN3o9()-364.0 -393.5 -241.8 0.0 0.0 Discipline General Chemistry O A. 500 The average bond energies in kJ/mol of the C-H, C-O, C-C, and O-N single bonds present in nitroglycerin are 413, 358, 347, and 201, respectively O B. 1000Explanation / Answer
The balanced chemical equation for the reaction is given as
4 C3H5N3O9 (l) --------> 12 CO2 (g) + 10 H2O (g) + 6 N2 (g) + O2 (g)
The decomposition of 2 moles of nitroglycerine is given as
2 C3H5N3O9 (l) --------> 6 CO2 (g) + 5 H2O (g) + 3 N2 (g) + ½ O2 (g)
The enthalpy change for the reaction is given as
?H0 = ?n.?H0f(products) - ?n.?H0f(reactants)
= [(6 moles CO2)*?H0f(CO2, g) + (5 moles H2O)*?H0f(H2O, g) + (3 moles N2)*?H0f(N2, g) + (1/2 mole O2)*?H0f(O2, g)] – [(2 moles C3H5N3O9)*?H0f(C3H5N3O9, g)]
= [(6 moles)*(-393.5 kJ/mol) + (5 moles)*(-241.8 kJ/mol) + (3 moles)*(0.0 kJ/mol) + (1/2 mole)*(0.0 kJ/mol)] – [(2 moles)*(-364.0 kJ/mol)]
= [(-2361 kJ) + (-1209 kJ) + (0.0 kJ) + (0.0 kJ)] – (-728 kJ)
= (-3570 kJ) – (-728 kJ)
= -3570 kJ + 728 kJ = -2842 kJ (ans).
The answer is close to -3000.0 kJ. I believe the question simply lists the numerical value and not the exact answer. The numerical value is close to 3000.0 kJ; however, I am assuming they haven’t included the sign of ?H0.