In: Chemistry
The decomposition of nitrosyl bromide is a second-order reaction: NOBr (g) à NO (g) + ½ Br2(g)
If the initial concentration of NOBr is 0.250 M, how much heat is evolved or absorbed per liter of solution in one minute? The rate constant is 0.80 L/(mol.s). The heats of formation are +82.2 kJ/mol for NOBr, +90.2 kJ/mol for NO, and +30.9 kJ/mol for Br2 as a gas.
Is a second order reaction so the equation you need to use is the following:
1/A = 1/Ao + kt
From here solve for A:
1/A = 1/0.250 + 0.80 * 60 = 52
A = 0.0192 mol/L
With the heat of formation, let's calculate rxn
rxn = prod - react
rxn = (90.2 + 30.9/2) - (82.2)
rxn = 23.45 kJ/mol
Finally, use the following expression to get the heat:
Q = rxn * [C]
Q = 23.45 kJ/mol * 0.0192 mol/L
Q = 0.45024 kJ/L or simply 450.24 J/L
Hope this helps