25.0 mL of nitrous acid (HNO2) is titrated with a 1.235 M solution of KOH. The equivalence point (stoichiometric point) is observed after 9.26 mL of base is added. What is the original concentration of the acid

0.456 M

Explanation:

Step 1: Write the balanced neutralization equation

HNO₂ + KOH ⇒ KNO₂ + H₂O

Step 2: Calculate the reacting moles of KOH

9.26 mL of 1.235 M KOH react.

0.00926 L × 1.235 mol/L = 0.0114 mol

Step 3: Calculate the reacting moles of HNO₂

The molar ratio of HNO₂ to KOH is 1:1. The reacting moles of HNO₂ are 1/1 × 0.0114 mol = 0.0114 mol.

Step 4: Calculate the initial concentration of HNO₂

0.0114 moles of HNO₂ are in 25.0 mL of solution.

[HNO₂] = 0.0114 mol / 0.0250 L = 0.456 M

it is the most commonly accepted one