A chemist investigates the thermal decomposition of at

CHEMISTRY · Multi-part · A Level · Chemistry · Rate equations · Rate equations

Problem

A chemist investigates the thermal decomposition of

\mathrm{N_2O_5(g)}

45^{\circ}\text{C}

. The concentration of the reactant is monitored over time, giving the data shown below.

Time (s)	0	100	200	300	400	500
$[\mathrm{N_2O_5}]$ (M)	0.400	0.285	0.203	0.144	0.102	0.072

Answer the following questions about the kinetics of this reaction. (a) Describe a graphical method that can be applied to the data to establish the reaction order with respect to

\mathrm{N_2O_5}

. State the reaction order indicated by the data and justify your conclusion based on the graph you would construct. (b) Using the data and the reaction order you identified, determine the numerical value of the half-life of the reaction at

45^{\circ}\text{C}

. Show all work including units. (c) Predict the concentration of

\mathrm{N_2O_5}

after

1.00\,\text{ks}

(

1000\,\text{s}

). Provide your reasoning and calculations. (d) Calculate the time required for the concentration of

\mathrm{N_2O_5}

to decrease to

5.0\%

of its initial value. (e) Explain how the constancy (or lack thereof) of the half-life you calculated in part (b) supports the reaction order conclusion from part (a).

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