Question

what is the hydronium ion concentration of a solution at 25°c with a poh of 7.9?
select the correct answer below:
1.259×10⁻⁸ m
7.943×10⁻⁷ m
3.707×10⁻⁴ m
2.243×10⁻³ m

Explanation:

Step1: Calculate pH

At \(25^{\circ}\text{C}\), \(pH + pOH=14\). Given \(pOH = 7.9\), then \(pH=14 - 7.9 = 6.1\)

Step2: Calculate hydronium ion concentration

The formula for \(pH\) is \(pH=-\log[H_3O^+]\). Rearranging for \([H_3O^+]\), we get \([H_3O^+]=10^{-pH}\). Substituting \(pH = 6.1\), \([H_3O^+]=10^{-6.1}\)
Using the property \(a^{m + n}=a^m\times a^n\), \(10^{-6.1}=10^{-7+0.9}=10^{-7}\times10^{0.9}\)
Since \(10^{0.9}\approx7.943\), \([H_3O^+]=7.943\times 10^{-7}\text{ M}\)

Answer:

\(7.943\times 10^{-7}\text{ M}\)