Answer to Question #152292 in General Chemistry for Nolha

Question

What is the hydronium-ion concentration in a solution formed by combining 750 mL of 0.10 M NaOH with 250 mL of 0.30 M HCl?
NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)

Answer 1

We find the moles first

(0.75×0.1)mol NaOH +(0.25×0.3)mol HCl

0.075 mol NaOH +0.075mol HCl

O.075mol/L ⁺NaOH+ 0.075mol/L HCl

0.075mol/L NaCl appears after the mixing

O.075M NaCl---------0.075M Na⁺ +0.075M Cl^-

0.075M Na⁺ +HOH----------no hydrolysis

0.075M Cl^- +HOH ------------no hydrolysis

Therefore the PH of the solution is determined by the ionisation of H₂O=H⁺ + OH^-

At 25°c the molar conc of pure water is

[H⁺]=[OH^-]=1×10^-7M

Since the conc of the reaction depends on water then the hydronium-ion concentration of the reaction is;

1×10^-7M