Turn on thread page Beta
    • Thread Starter
    Offline

    14
    ReputationRep:
    would it be correct to say that:

    alkalis dissociate in acids AND water
    bases dissociate in acids only
    • Community Assistant
    • Study Helper
    Offline

    17
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by medhelp)
    would it be correct to say that:

    alkalis dissociate in acids AND water
    bases dissociate in acids only
    no, they both react with acids.
    Offline

    12
    ReputationRep:
    Alkalis are soluble bases. Bases react with acids to neutralise them
    • Thread Starter
    Offline

    14
    ReputationRep:
    (Original post by charco)
    no, they both react with acids.
    so why do we make the distinction of alkalis being soluble

    surely to react with an acid they have to dissociate in the acid then the ions react?
    • Community Assistant
    • Study Helper
    Offline

    17
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by medhelp)
    so why do we make the distinction of alkalis being soluble

    surely to react with an acid they have to dissociate in the acid then the ions react?
    Not so.

    Metal oxides are classified as bases, but most are totally insoluble. Copper(II) oxide reacts with acids forming salts and water, but it is insoluble in water.

    The distinction is pretty meaningless, but you can consider a soluble base to be an alkali.
    • Thread Starter
    Offline

    14
    ReputationRep:
    (Original post by charco)
    Not so.

    Metal oxides are classified as bases, but most are totally insoluble. Copper(II) oxide reacts with acids forming salts and water, but it is insoluble in water.

    The distinction is pretty meaningless, but you can consider a soluble base to be an alkali.

    could you help me with another question as well, please?


    the answer is c - 3 but i don't get how, I keep getting either 1 or 5 as my answer?

    Spoiler:
    Show




    this is how I tried

    method 1:

    cobalt has 27 electrons
    1s2 2s2 2p6 3s2 3p6 4s2 3d7
    therefore cobalt 2+ is 3d5 which is a half filled shell so all 5 are unpaired?


    method 2:
    GCSE electron configurations

    27 in cobalt so 25 in cobalt 2+

    25 -2 for inner shell = 23
    23/ 8 per shell = 2 full shells with 7 remaining in outer shell
    7 into 3 pairs with 1 unpaired


    Offline

    19
    ReputationRep:
    (Original post by medhelp)

    method 1:

    cobalt has 27 electrons
    1s2 2s2 2p6 3s2 3p6 4s2 3d7
    therefore cobalt 2+ is 3d5 which is a half filled shell so all 5 are unpaired?
    There's your mistake.
    • Community Assistant
    • Study Helper
    Offline

    17
    ReputationRep:
    Community Assistant
    Study Helper
    To add to Alow's post, it is always the 4s electrons that are lost first ...
    • Thread Starter
    Offline

    14
    ReputationRep:
    (Original post by charco)
    To add to Alow's post, it is always the 4s electrons that are lost first ...
    why are 4s lost first, I thought 3d was a higher energy level?
    • Community Assistant
    • Study Helper
    Offline

    17
    ReputationRep:
    Community Assistant
    Study Helper
    (Original post by medhelp)
    why are 4s lost first, I thought 3d was a higher energy level?
    OK, the real reason why is complex and the domain of university level treatment of orbitals. (Alow can do the honours if he so chooses - I won't)

    The "accepted A' level" reason is that the 4s and 3d levels are very close in energy, but the occupation of the 3d level lowers its energy wrt the occupied 4s level.

    So, when filling up, the 4s fill before the 3d and when losing electrons the 4s are removed before the 3d.

    Chromium, d5, and copper, d10, are however, exceptions as the 4s only singly occupies while the 3d is half-full and full respectively.

    When you get the the second and third row TMs the whole thing is thrown into a cocked hat, so just consider yourself fortunate that you only have to deal with 1st row TMs.
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: August 21, 2017

2,627

students online now

800,000+

Exam discussions

Find your exam discussion here

Poll
Should predicted grades be removed from the uni application process

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.