ocr a f325 revision thread

Suggest why a reactive metal such as Zinc is a powerful reducing agent.

Because the oxidation number of zinc increases and hence is a poweful oxidising agent

I'm sorry, but not quite, although you're right about the ability of the oxidation state of Zinc to increase.

Basically, reactive metals such as Zinc are able to readily donate electrons to species, and reducing them as a result. For this reason, Zinc and other reactive metals are powerful oxidising agents

So literally you want the definition of reaching agent

Well, yes and no, it does involve applying the definition of a reducing agent because I asked why reactive metals such as Zinc are powerful reducing agents. :P

I see thanks



Suggest why scientists now a days believe that PH has been associated in giving inaccurate PH values and give an example of how PH can be measured (3)

No worries

pH can be measured using a pH probe. Hmm, finding the first part difficult, but is it because there are other things that cause acidity as well as H+? I have no idea, just a guess, sorry about that :P

Correct for how to measure, yes nearly for your second point , I was thinking along the lines that because when an acid also dissociates it releases alkali ions/groups which can affect the PH so is not always accurate


please tell me if I am wrong because I made these questions myself

It's okay, you know what you're talking about!

That makes perfect sense, thanks!

Why can enthalpy change of solutions sometimes be exothermic, even though bonds are broken (so theoretically it should be endothermic all the time)?

Thanks


Enthalpy changes of solution can be exothermic because it releases energy as bonds are being formed between the ionic compound and water molecules and is endothermic when energy is absorbed in order to break the strong forces of attraction between the ions and water molecules so energy is needed to break bonds so endothermic.

Yes that is correct Although, one thing with respect to wording, instead of saying the ionic compound bonds to water molecules, it may be a good idea to specify that it's the ions of the ionic compound. I'm sorry, it's very picky, but I don't know whether examiners would be picky over that, but I don't mean it in a bad way

I'm sorry if I take a while to reply now, although I will reply when I'm online of course.

Good luck with your revision!

No worries , you are doing a goof thing , I like it ,thankyou

Define:Kc

Hi everyone, is the catalyst in a mutlistep reaction included in the rate equation? I just did a question and it was apprently.... :/

Anyone got some good resources for questions as I don't want to finish the past papers too quickly :-/


Posted from TSR Mobile

Have you seen some of the legacy papers on the OCR website (they should be on the same page as the link to the other past papers)? If you haven't seen them already, there are some legacy papers on the OCR website (papers from the previous spec), which do contain some questions that are relevant to our current spec.

http://www.ocr.org.uk/qualifications/as-a-level-gce-chemistry-a-h034-h434/

- Past papers -> Legacy qualification.

I hope you find them useful!

Thanks, I shall have a look at those over the half term and would you be able to help me with a question?

Okay no worries I would be happy to give it a try, fire away