I have a chemistry problem, Can anyone help me?

Question

I really don't understand this question:
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In a 1L flask filled with NO2 at 1 atm presure, the content of dinitrogen tetroxide was 0.00027 mol after 15 s. Calculate the reaction rate. In a second experiment, at 2 atm of pressure, the N2O4 content after 15 s was 0.00108 mol. Write the rate law.

Answer 1

The key to this question is knowing the following equation:

2NO2 ----> N2O4.

N2O4 is called dinitrogen tetroxide. It starts off at 0 mol, so you can work out how fast it forms.

You can compare how fast the N2O4 forms after doubling the initial pressure (the same as concentration) of NO2, to see the order of the reaction with respect to NO2.