what is the hydronium ion concentration in a solution formed by combining 750mL of 0.10M NaOH with 250mL of 0.30 M HCl

Explanation:

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In this case, since the reaction between sodium hydroxide and hydrochloric acid has a 1:1 mole ratio between them:

In order to compute the hydronium H⁺ concentration in the mixed volumes of the given solutions we first compute the moles of each reactant:

As seen, since those amounts are the same, we infer all the acid and base are consumed so the pH is 7 because a neutral salt is produced, and the corresponding H⁺ concentration is:

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