What is the hydroxide-ion concentration in a solution formed by combining 200. ml of 0.16 m hcl with 300. ml of 0.091 m naoh at 25oc? hcl (aq) + naoh (aq) → nacl (aq) + h2o (l) ?

The acid base reaction equation is as follows;

HCl + NaOH - - - > NaCl + H₂O

stoichiometry of HCl to NaOH is 1:1

NaOH is a strong base and HCl is a strong acid they completely dissociate into its ions

number of HCl moles - 0.16 mol/L x 0.200 L = 0.032 mol

number of NaOH moles - 0.091 mol/L x 0.300 L = 0.0273 mol

Limiting reactant is NaOH therefore number of HCl moles reacted - 0.0273 mol

the excess amount of HCl moles are - 0.032 - 0.0273 = 0.0047 mol

since HCl is a strong acid

total volume - 200 mL + 300 mL = 500 mL

[HCl ] = [H⁺]

therefore [H⁺] = 0.0047 mol / 0.500 mL

[H⁺] = 0.0094 mol/L

hydroxide ion concentration - 0.0094 M