## 9C. 3

Kelly Cai 4D
Posts: 55
Joined: Sat Jul 20, 2019 12:17 am

### 9C. 3

What is the formula for

(a). potassium hexacyanidochromate (III)

Shimei_2F
Posts: 100
Joined: Fri Aug 09, 2019 12:17 am

### Re: 9C. 3

K3[Cr(CN)6]

Alex Tchekanov Dis 2k
Posts: 118
Joined: Sat Aug 24, 2019 12:16 am

### Re: 9C. 3

The way that you can deduce this formula from the name is that first it starts with potassium - K, you don't know how many yet, but you know the first atom is K, and because K is a positive cation, it is outside of the brackets. Then for hexacyanido - hexa means 6 and cyanido means CN-. Then you have Cromate which means the chromium atom. So far now you have K [Cr(CN)6] - but how do we know how many K's there are? That's solved by the roman numerals that are in the name, Chromate (III). This means that chromium has a 3 plus charge, and we already know that CN has a minus one charge. Since the next compound is neutral that means we need to have 3 K+ ions to balance out the charges. Hopefully that helped.