Knowing whether the compound has net neutral charge or not

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Alexandra Bowling 1K
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Joined: Fri Sep 26, 2014 2:02 pm

Knowing whether the compound has net neutral charge or not

Postby Alexandra Bowling 1K » Tue Dec 02, 2014 6:21 pm

For quiz 3 prep #4, you have to find the chemical formula for potassium tetracyanonickelate (II). I know that it should be K2[Ni(CN)4], but why? I know the following:

(CN)4= (-1)x4=-4
Ni (II)=+2

Thus, the charge of the coordination compound is -2, and making potassium K2 instead of K neutralizes the whole compound. But how do you know when you're supposed to neutralize the compound? How can you tell from the formula whether or not the whole compound should have a net negative charge or not?

K Honeychurch 1K
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Joined: Fri Sep 26, 2014 2:02 pm

Re: Knowing whether the compound has net neutral charge or n

Postby K Honeychurch 1K » Tue Dec 02, 2014 7:42 pm

I think the problem would have to specify that the compound has a charge, otherwise you can assume the total charge is 0. Also, I don't think we've had a problem in which the compound has a charge.

Justin Le 2I
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Joined: Fri Sep 26, 2014 2:02 pm

Re: Knowing whether the compound has net neutral charge or n

Postby Justin Le 2I » Tue Dec 02, 2014 9:58 pm

If the compound has a charge, it will say "ion" at the end in the name.

GinaYoung1L
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Re: Knowing whether the compound has net neutral charge or n

Postby GinaYoung1L » Wed Dec 03, 2014 10:39 am

A coordination compound is always electrically neutral. It includes the complex (metal and ligands inside the brackets) and any outside ions. Therefore, it is not the coordination compound that has the -2 charge, it is the complex. Complexes (only the stuff inside the brackets) can be neutral, anionic, or cationic. It is anionic if there is an -ate attached to the end of the metal's stem name.

Alexandra Bowling 1K
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Joined: Fri Sep 26, 2014 2:02 pm

Re: Knowing whether the compound has net neutral charge or n

Postby Alexandra Bowling 1K » Wed Dec 03, 2014 12:37 pm

But if it does have "ion" at the end of the name, how are you supposed to figure out the positive or negative charge?

Valeria Mazzanti 3H
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Joined: Fri Sep 26, 2014 2:02 pm

Re: Knowing whether the compound has net neutral charge or n

Postby Valeria Mazzanti 3H » Wed Dec 03, 2014 9:11 pm

They would probably have to specify the charge it has.

thuyphuong1I
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Joined: Fri Sep 26, 2014 2:02 pm

Re: Knowing whether the compound has net neutral charge or n

Postby thuyphuong1I » Wed Dec 03, 2014 9:21 pm

If it is an ion, you can usually tell it has a negative charge if "-ate" is added to the end of the metal. You can also determine charge by assigning charges to each element in your complex, given ligands with their prefixes (if any) and the transition metal with its oxidation number, and then adding them up.
Last edited by thuyphuong1I on Wed Dec 03, 2014 10:06 pm, edited 1 time in total.

Justin Le 2I
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Joined: Fri Sep 26, 2014 2:02 pm

Re: Knowing whether the compound has net neutral charge or n

Postby Justin Le 2I » Wed Dec 03, 2014 9:45 pm

Gina Young is correct. My previous comment should only apply to complexes.


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