Question

Picric acid (C6H3N3O7) is a dangerous explosive that detonates according to the following balanced reaction equation. The production of solid carbon gives the explosion a sooty appearance.

2C6H3N3O7(s) 3N2 (g) + 11CO(g) + 3H2O(g) +C(s) ΔH=-1724.5kJ/mole
A 138. g block of dry picric acid has a volume of about 60 mL. The block was detonated outdoors at 1.00 atm at a

temperature of 298 K.

a. Assuming the C (s) produced has a negligible volume, and that the reaction occurs at constant temperature, how much work is done by the detonation of the 138. g block of picric acid described above?

b. How much heat is released by the detonation of the 138. g block of picric acid described above? c. Estimate ΔE for the reaction in kJ/mole.

Answer 1

a) moles of picric acid = mass / molar mass of picric acid = 138 /229.1 = 0.60236

Moles of gas ( CO + H2O) produced per 1 mole picric aci = ( 11+3) /2 = 7

moles of gas produced per 0.60236 moles acid = 0.60236 x 7 = 4.2165

Volume of gas = nRT /P   = ( 4.2165x0.08206x298) /1= =103.1 L

Work done = P x dV = 1 atm x 103.1 L = 103.1 atmliter = 103.1 x101.325 J ( 1 atm liter = 101.325 J)

            = 10447.6 J = 10.45 KJ

b) Heat released = dH x moles = -1724.5 x 4.2165 = - 7271.35 KJ ( -ve sign indicates heat released)

c) dE reaction = dQ + dW = -7271.35 -10.45 = - 7281.8 KJ