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RXNs of inorganic metals ionic eqs

http://filestore.aqa.org.uk/subjects/AQA-CHEM5-QP-JUN15.PDF

For question 7, I don't quite understand/appreciate how to write the ionic equation for these reactions. Surely the 'normal' equations can't be simplified?

I would have said

[Cr(H2O)3(OH)3] + 3H+ ---> [Cr(H2O)6]3+ + 3OH-

and

[Cr(H2O)3(OH)3] + 3OH- ---> [Cr(OH)6]3- + 3H2O

????

Thanks

Reply 1

GDN

Original post by hi-zen-berg

Your equations are fine - they are the ionic equations

Reply 2

hi-zen-berg

Original post by GDN

Your equations are fine - they are the ionic equations

Thanks for the feedback; I thought so but the mark scheme doesn't seem to agree with me? Quoting

Cr(OH)3 + 3H2O + 3H+ → [Cr(H2O)6]3+

and

Cr(OH)3 + 2H2O + OH– → [Cr(H2O)2(OH)4]–

Reply 3

GDN

Original post by hi-zen-berg

Thanks for the feedback; I thought so but the mark scheme doesn't seem to agree with me? Quoting

Cr(OH)3 + 3H2O + 3H+ → [Cr(H2O)6]3+

and

Cr(OH)3 + 2H2O + OH– → [Cr(H2O)2(OH)4]–

AQA accepts a variety of equations for these changes - in my opinion yours are the most consistent since they emphasise that the various species are 6 coordinate