Reaction rate, rate equation and half life

[Sabra_a]

Summary: Hydrogen peroxide, H2O2, decomposes as per following reaction scheme:
H2O2(l) → H2O(l) + O2(g)
The concentration versus time data for the decomposition of hydrogen peroxide is given in Table 1.

i) Calculate the reaction rate constant, k, graphically, with the aid of Excel software. Confirm that this is a first-order reaction.
ii) Write the rate equation for the given reaction.
iii) Calculate the half-life for hydrogen peroxide.

I have attached the table and my attempt to solve the question, a feedback will be appreciated. I'm quite stuck on the 2nd and 3rd point

 

[epenguin]

This ought to be on the homework help, it is so elementary.
The only hard part is question i) which you or someone seems to have solved already.
The answer to ii) is already in the answer given, you only know need to know what "rate equation" means. See your textbook or Wikipedia.
iii) is almost contained in your answer. [A₀] Is the starting concentration of H₂O₂, so when only half of that is left, what will your fourth equation give you?

 

[Sabra_a]

thank you, for point ii) I wasn't sure about the answer because I thought I answered it in the first part. I rearranged my answers.

 

[epenguin]

Looks OK to me.
I guess 1st order rate constants are officially most often quoted in s^-1 though 'at home' in the lab you can find minutes/hours/days convenient..

 

[Sabra_a]

Thank you