Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter

    I've never really though about this until now.
    When a question says something like, a 30cm3 sample is diluted by 50cm3 water, find the pH of the solution formed.
    Should you take into account the moles of H+ that is in the water that is added (1) or would you just assume that the water doesn't dissociate at all (2). I have always assumed it is the latter but when thinking about it to get a more accurate answer you should consider the dissociation of water right? I know to 2dp it wouldn't usually make any difference but t would lose method marks right.
    Which one is correct and more importantly which one should I use in an exam?

    pH calcs will always be done at concs so low that you can forget about the ionisation of water.

    Use your latter thought, esp. in exams.
Do you agree with the PM's proposal to cut tuition fees for some courses?

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