The following data were obtained for the gasphase decomposition of dinitrogen pentoxide.
2 N2O5(g) → 4 NO2(g) + O2(g)
[N2O5]0
(mol/L) Initial Rate
(mol/L·s)
0.0750 8.90* 104
0.190 2.26* 103
0.275 3.26* 103
0.410 4.85* 103
Defining the rate as −Δ[N2O5]/Δt, How do I determine the rate law?
What is the value of the rate constant?
Please and Thank you. : )
1 Answer

[N2O5]º(M)…..Initial Rate(M/s)
0.0750…………….8.90×104
0.190………………2.26×103
0.275………………3.26×103
0.410………………4.85×103
to determine the rate constant, you first have to determine the rate order. with the balanced equation, it appears that is it second order due to 2 moles N2O5 being present.
when we compare rate2 to rate1, we see that x, the exponent, = 1 so the reaction is first order
rate2 = 2.26×10^3 = k(0.19)^x
——————————————–
rate1 = 8.9×10^4 = k(0.075)^x
2.54 = 0.19^x/0.075^x
ln2.54 = x(ln(0.19/0.075))
0.932 = x(0.93)…..x = 1
reaction is first order
rate = k[N2O5]
8.9×10^4 = k (0.075M)…..k = 0.0119