Hey!
Welcome to the forums
Looking at your research question, I think you're on the right path but it's phrased a little bit awkwardly e.g. are you measuring the concentration or the volume of hydrogen gas?
Throughout your text make sure you also check your use of capitalisation is correct.
For your rationale in particular,
> consider starting more broadly (with redox in general) before narrowing down on your experiment
> the "(electrode reduction potential)" being listed after the full stop is place a bit awkwardly. I recommend either moving this before the full stop, removing it, or expanding it out into a full sentence.
> Your rationale implies that you want to know about rate of reaction (how are you measuring this) whereas your research question refers to concentration of hydrogen gas.
> be careful - amount and concentration aren't the same thing
> Consider including the redox equation you are investigating -> use the equation to help you describe the theoretical relationship
> The reference to oxidation levels of magnesium is confusing - are you saying this in terms of knowing much much magnesium has reacted?
Methodology:
> The first sentence doesn't say much of anything, consider starting out by describing the original experiment.
> You may some good points, but consider using less-loaded and more precise terms like "qualitative" rather than "purely subjective"
see also: "unreliable", "imprecise" etc. rather than "uncredible"
> Be careful with tense
> This looks unfinished - make sure you don't forget to come back to it
I hope you find this helpful!
best of luck