If the pH of a solution is 4.66, what is the `[H3O^+]` ?

The pH of a solution is a measure of the hydronium ion concentration. The hydronium ion is represented as `H_3O^+` . Mathematically, the relationship between hydronium ion concentration and pH can be written as:

`pH = -log_(10) [H_3O^+]`

This equation can be further written as:

`[H_3O^+] = 10^(-pH)`

In this case, pH = 4.66.

Therefore, the hydronium ion concentration can be calculated by substituting the value of pH in the above equation.

That is, `[H_3O^+] = 10^(-4.66) = 2.19 xx 10^(-5) M`

Thus, the given solution contains 2.19 x 10^-5 M hydronium ions.

We can also calculate the pOH of the solution by using the relation: 

pH + pOH = 14

This equates to: pOH = 14-4.66 = 9.34

We can also calculate [OH^-] by using the relation:

`pOH = -log_(10)[OH^-]`

Solving this equation, we get [OH^-] = 4.57 x 10^-10 M.

Hope this helps.