Question

calculate [h3o ] in the following aqueous solution at 25 ∘c : [oh−]= 1.5×10−9 m . express your answer using two significant figures.

Answer 1

The concentration of hydronium ions ([H3O+]) in the solution is approximately 6.67 x 10^-6 M, rounded to two significant figures.

To calculate the concentration of hydronium ions ([H3O+]) in an aqueous solution at 25°C when the concentration of hydroxide ions ([OH-]) is given, you can use the following equation:

Kw = [H3O+][OH-]

where Kw is the ion product of water at 25°C, which is approximately 1.0 x 10^-14 (at this temperature).

Given [OH-] = 1.5 x 10^-9 M, you can rearrange the equation to solve for [H3O+]:

[H3O+] = Kw / [OH-]

[H3O+] = (1.0 x 10^-14) / (1.5 x 10^-9)

[H3O+] ≈ 6.67 x 10^-6 M

So, the concentration of hydronium ions ([H3O+]) in the solution is approximately 6.67 x 10^-6 M, rounded to two significant figures.

Answer 2

Taking into account the definition of pH and pOH, the [H₃O⁺] is 6.61×10⁻⁶ M.

}pH is a measure of acidity or alkalinity that indicates the amount of hydrogen ions present in a solution or substance.

The pH is defined as the negative base 10 logarithm of the activity of hydrogen ions, that is, the concentration of hydrogen ions or H₃O⁺:

pH= - log [H⁺]= - log [H₃O⁺]

Similarly, pOH is a measure of hydroxyl ions in a solution and is expressed as the logarithm of the concentration of OH⁻ ions, with the sign changed:

pOH= - log [OH⁻]

The following relationship can be established between pH and pOH:

pOH + pH= 14

Being [OH⁻]=1.50×10⁻⁹ M, the pH is calculated as:

pOH= - log (1.50×10⁻⁹ M)

Solving:

pOH= 8.82

Taking into account the relationship between pH and pOH, pH is calculated as:

pH + 8.82= 14

pH= 14 - 8.82

pH= 5.18

Replacing in the definition of pH the concentration of H₃O⁺ ions is obtained:

- log [H₃O⁺]= 5.18

Solving

[H₃O⁺]= 10⁻⁵ ¹⁸

[H₃O⁺]= 6.61×10⁻⁶ M

In summary, the [H₃O⁺] is 6.61×10⁻⁶ M.