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# Help with this equation watch

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1. Oxidising Iron(ii) to Iron(iii) ions using a solution of Cr2O7 2- ions, acidifed with dilute sulphuric acid; the chromium ends up as Cr3+ ions.

I have done some and got half the right answer but I don't know the actual logical steps required to get the full answer correct for this type of question.
2. Fe^2+ --> Fe^3+ + e^-
14H^+ +Cr2O7^2- + 6e^- ---> 2Cr3+ + 7H2O
Then multiply Fe by 6 to get equal number of electrons and add them together and cancel down to get the overall equation (btw is this CH5?
3. (Original post by Ahmed766)
Fe^2+ --> Fe^3+ + e^-
14H^+ +Cr2O7^2- + 6e^- ---> 2Cr3+ + 7H2O
Then multiply Fe by 6 to get equal number of electrons and add them together and cancel down to get the overall equation (btw is this CH5?
No idea what you mean about C5? I am gonna use its for F325 and 6 for OCR a2 chem, just like a couple of marks worth but I found the question Jim Clark chemistry book.

Thanks for the answer ill check it out properly after I eat lunch right now.
4. Double post.
5. (Original post by Ahmed766)
Fe^2+ --> Fe^3+ + e^-
14H^+ +Cr2O7^2- + 6e^- ---> 2Cr3+ + 7H2O
Then multiply Fe by 6 to get equal number of electrons and add them together and cancel down to get the overall equation (btw is this CH5?
Ok I got it now. Thanks.
But what is this type of question called? If you don't mind telling me. Like what told you to use this method to work it out? Or did you just see it and now it was this method or is this the only method to work it out?
6. This is balancing hg equations, I finished A2 chemistry this year and this is only way to do it that I'm aware of. I did it thus way because that is just how I know how to do it, first balance the metals on both sides then the Oxygen by adding H2O to the opposite side, then add H+ opposite the water to balance the Hydrogen in the water. Last but most importantly balance the charges to equal each other on both side by adding electrons and continue like above
7. (Original post by Ahmed766)
This is balancing hg equations, I finished A2 chemistry this year and this is only way to do it that I'm aware of. I did it thus way because that is just how I know how to do it, first balance the metals on both sides then the Oxygen by adding H2O to the opposite side, then add H+ opposite the water to balance the Hydrogen in the water. Last but most importantly balance the charges to equal each other on both side by adding electrons and continue like above
Ok thanks man!
I did the next one and got it right, following the method.
I did A2 chem and failed(C) as I didn't revise that much so im going back to the basics and really learning it properly. Thanks a lot bro for the help.
8. Anytime, you absolutely did not fail don't be silly! Chemistry is one of the hardest A levels if not the hardest, it requires z lot of work. If there's anything else I can do to help I'm just a pm away.
9. TRANSMITTER RANGE (10 points possible)
Imagine that we intend to communicate with a newly discovered civilization. They are at a distance of 87 light years from us.

If their radio receivers are similar to ours, they will be able to detect signals of about 8×10−33 watts per square meter. We will need to build a transmitter powerful enough that our signal will have this intensity when it arrives.

If we have built the transmitter correctly, we should be able to tell based on the intensity of the radio waves near the transmitter. What intensity should we expect the radio waves have at a distance of 1 meter from the transmitter?

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Updated: November 21, 2015
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