Final answer:
The concentrations of hydronium ion and hydroxide ion can be calculated for solutions at 25°C using the ion-product constant for water, Kw. In pure water, both ions have a concentration of 1.0 × 10−7 M. When one ion concentration is given, the other can be found using the formula Kw = [H3O+][OH−].
Step-by-step explanation:
The subject of this question is calculating the concentrations of hydronium ion and hydroxide ion in aqueous solutions at 25°C, which falls under the Chemistry category. This type of question is typically encountered at the High School level. In pure water at 25°C, the concentrations of both hydronium ions (H3O+) and hydroxide ions (OH−) are equal, since water is neutral. They have a concentration of 1.0 × 10−7 M, due to the self-ionization of water, where water molecules dissociate slightly to form H3O+ and OH−.
For a solution with a given hydronium ion concentration, the hydroxide ion concentration can be calculated using the ion-product constant for water (Kw) at 25 °C, which is 1.0 × 10−14. Hydronium ion concentration and hydroxide ion concentration are inversely proportional in an aqueous solution, as indicated by the formula Kw = [H3O+][OH−].
For instance, with a hydronium ion concentration of 4.5 × 10−5 M, the hydroxide ion concentration can be found by dividing Kw by this given concentration. Similarly, if the hydroxide ion concentration is known (such as 7.5 × 10−2 M), one can find the hydronium ion concentration by taking Kw and dividing it by the given hydroxide concentration.