CHEM P12(mcq) help

[anahita16]

Hello!

I thought about posting my query in the main chemistry thread but was too afraid it would get lost in the swarm of questions over there. I have my chemistry paper coming on wednesday, so I'll probably be asking lots more question. Please do help me.

By the way, as you'll soon realise from the nature of my questions, I'm pretty weak in chemistry and am a nightmare for all the chem teachers I've had so far.

Hope you'll all bear with me!

 

[anahita16]

Question number ONE...

A sample of 10cm3 of 0.1M iron(II) sulfate is titrated against 0.025M potassium manganate(VII) in the presence of an excess of fluoride ions. It is found that 10cm3 of the manganate(VII) solution is required to reach the end-point.
What is the oxidation number of the manganese at the end-point?
(M means mol per dm3)
Guys, how do I know where to start from? What's happening to the Fe2+? Oxidised/reduced? How to start such questions? Why is there a mention of fluoride ions?

I've only been able to calculate the number of moles of iron(II) sulfate-0.001 and KMnO4- 0.00025mol(hehe, maths!). Now what do I do with them? :%)

 

[sweetiepie]

Some Helpful Notes For Chemistry Paper 1!!!
http://www.creative-chemistry.org.uk/al ... /index.htm

Chemistry Reagents and conditions for reactions in organic chemistry
viewtopic.php?f=26&t=7013

Organic chemistry mindmap
viewtopic.php?f=26&t=8477

Tips for #31-40 Chemistry MCQs
viewtopic.php?f=26&t=9156

 

[anahita16]

It's not among the last 10 quesitons(31 to 40)
A +2
B +3
C +4
D +5

Correct answer is B.
But I don't know how.