Question

What is the apparent oxidation state of the K element in the compound $KHC{O}_3$ ?
A) +1
B) +2
C) +3
D) +4
E) +5

Answer 1

Hint: The answer to this question lies in the fact about calculation of oxidation based on its formula which includes writing the known oxidation states of bicarbonate ion and finding the oxidation state of carbonate ion.

Complete step by step solution:
We have come across the chapters in chemistry which includes the basic topic about finding the oxidation state of a central metal atom based on the known oxidation states.
Let us now refresh those calculation methods used for the calculation of oxidation states of the unknown atom.
- To start with, oxidation number is nothing but it is the state which indicates the degree of oxidation for an atom and is a hypothetical charge present on the atom which is usually represented by integers that can be positive, negative as well as zero.
- Oxidation number can also be defined as ‘total number of electrons that an atom can either gain or lose to form a chemical bond with the other atom’.

Now, to find the oxidation state of potassium in potassium bicarbonate we have to write the formula accordingly.
- For $KHC{O}_3$, Hydrogen has +1 charge and carbonate ion has -2 charge.
Since the whole compound is neutral and considering oxidation state of potassium as ‘x’ we have,
$$x+1+(-2)=0$$
$$\begin{array}{rl}& \Rightarrow x-1=0\\ & \Rightarrow x=+1\end{array}$$
So, the correct answer is “Option A”.

Note: Note that the oxidation number for a free element will always be zero, that is the elemental form always has zero oxidation state whereas when combined with other atoms, it can change the oxidation states. This fact helps you to lead to the correct answer.