## Hw 9c.1 part c

WYacob_2C
Posts: 102
Joined: Sat Jul 20, 2019 12:16 am

### Hw 9c.1 part c

For [Co(CN)5(OH2)]2-,
why is it called aquapentacyanocobaltate(III) ion instead of aquapentacyanocobalt(III) ion?

ShravanPatel2B
Posts: 100
Joined: Fri Aug 30, 2019 12:18 am

### Re: Hw 9c.1 part c

When the coordination compound has a negative charge we would usually add the suffix -ate to the Lewis Acid

curry 1E
Posts: 55
Joined: Wed Sep 18, 2019 12:15 am

### Re: Hw 9c.1 part c

Why is it colbalt (III)? What is the oxidation number of the metal?

WYacob_2C
Posts: 102
Joined: Sat Jul 20, 2019 12:16 am

### Re: Hw 9c.1 part c

curry 1E wrote:Why is it colbalt (III)? What is the oxidation number of the metal?

Cobalt has an oxidation number of 3+ because we see that there is an overall charge of 2-, there are 5 CN- molecules and 5 OH2 molecules. Because CN has a charge of -1, there is a total -5 charge from them alone. OH2 has no charge so we can ignore it. We are left with Co and we need to find its oxidation number, so we can set everything equal to -2 which is the overall charge.
Co + 5(CN-) + 5(OH) = -2
Co + 5(-1) + 5(0) = -2
Co - 5 + 0 = -2
Co = 5 - 2
Co = +3
Therefore, cobalt has an oxidation number of 3+.

Aprice_1J
Posts: 55
Joined: Wed Sep 18, 2019 12:16 am

### Re: Hw 9c.1 part c

Why is it aqua instead of hydroxide? Where does the OH get the extra hydrogen from?

AKhanna_3H
Posts: 104
Joined: Wed Sep 18, 2019 12:19 am

### Re: Hw 9c.1 part c

The formula gives us (OH2) which indicates aqua, if it was (OH), that would be hydroxido