Turn on thread page Beta
 You are Here: Home

# A-level chemisty : moles! i need some serious help :( watch

1. i have a question : calculate the number of atoms of O2 in 0.37 mol of KMnO4??

so far i have done: 6.02x10^23 x 0.37... but now what? do i multiply by 4??

please help me
2. Wrong forum. Try here:

http://www.thestudentroom.co.uk/forumdisplay.php?f=130
3. Shouldn't the question be asking for the number of molecules of O2?
Anyway, in each mole of the KMnO4, there are two moles of O2, shown by the "O4" in the molecular formula. So, in 0.37 moles of KMnO4, there'll be 0.37 x 2 = 0.74 moles of O2. Then just multiply that by Avogradro's constant, and you've got the number of molecules of O2.
4. so if the question had the formula KMnO2 for example, i wouldnt have to times by 2?
and sorry if this is the wrong forum, i literally just joined and have no idea what im doing, but thanks for directing me the right way
5. (Original post by emily00flowerpot)
so if the question had the formula KMnO2 for example, i wouldnt have to times by 2?
and sorry if this is the wrong forum, i literally just joined and have no idea what im doing, but thanks for directing me the right way
No; that'd mean that, in every mole of KMnO2, there was 1 mole of O2; so in 0.37 moles of KMnO2, then there'd be 0.37 moles of O2, due to the 1:1 ratio.
6. (Original post by Revolution is my Name)
No; that'd mean that, in every mole of KMnO2, there was 1 mole of O2; so in 0.37 moles of KMnO2, then there'd be 0.37 moles of O2, due to the 1:1 ratio.
so i go by the molar ratio?
7. (Original post by emily00flowerpot)
so i go by the molar ratio?
Well, yes, how many moles of the substance being asked about are in each mole of the substance you're being given information about, which is the only way to do it really.
8. (Original post by Revolution is my Name)
Well, yes, how many moles of the substance being asked about are in each mole of the substance you're being given information about, which is the only way to do it really.
ahh thank you so much

Reply
Submit reply
Turn on thread page Beta

### Related university courses

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: January 30, 2010
Today on TSR

### He broke up with me because of long distance

Now I'm moving to his city

### University open days

1. University of Bradford
University-wide Postgraduate
Wed, 25 Jul '18
2. University of Buckingham
Psychology Taster Tutorial Undergraduate
Wed, 25 Jul '18
3. Bournemouth University
Clearing Campus Visit Undergraduate
Wed, 1 Aug '18
Poll

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.