Question

What is the formula of the compound cesium trichloro fluoro iodate $(III)$ ?
a.) $[Cr{(N{H_3})_5}Cl]S{O_4}$
b.) $Cs[IC{l_3}F]$
c.) $Cs[IC{l_2}F]$
d.) None of the above

Answer 1

Hint: The compound has cesium so the cesium is written as Cs. As there is “trichloro”, that means there will be three chloride ions and will have one fluorine because it is mentioned as “fluoro” in the name of the compound.

Complete step by step answer:
- In option (A), there is $Cr$.
$Cr$ is written for the Chromium element. But in the given question, cesium is given, not chromium. Also, there is $N{H_3}$ and $S{O_4}$ present in the compound , it is written for ammonia and sulphate respectively. But there is no such element written in the given question. That’s why it is an incorrect option.
- In option (B) , there is $Cs$. It signifies cesium element. There are three chloride ions corresponding to “trichloro” and one fluoride ion corresponding to “fluoro” given in the question. Here, cesium is in $ + 1$ state. That means ${[IC{l_3}F]^ - }$ has one negative charge. Chlorine and fluorine have $ - 1$ oxidation state respectively.
Let’s assume that the oxidation number of iodine is $x$ here.
$
[3*( - 1)] + ( - 1) + x = - 1 \\
x = + 3 \\
$
Iodine is in $ + 3$ oxidation state . Hence, there will be written iodate $(III)$ at the end of the naming of the compound. That’s why it’s written as cesium trichloro fluoro iodate $(III)$. Hence, it is the correct option.
- In option (C), there are two chloride ions written. That’s why it is incorrect.
The correct option is option “B” .

Note: In coordination compounds, compounds are written in such a way, where the part in the third bracket is known as coordination sphere and the remaining part is known as ionic sphere. And the formula is identified mostly by the name given.