Determining Original Concentration of Nitrous Acid (HNO₂) Through Titration
How can we determine the original concentration of nitrous acid (HNO₂) through titration?
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?
Answer:
0.456 M
To determine the original concentration of nitrous acid (HNO₂) through titration, we first need to write the balanced neutralization equation for the reaction between nitrous acid and potassium hydroxide (KOH):
HNO₂ + KOH ⇒ KNO₂ + H₂O
Next, we calculate the reacting moles of KOH used in the titration:
9.26 mL of 1.235 M KOH react.
0.00926 L × 1.235 mol/L = 0.0114 mol
Then, we determine the reacting moles of nitrous acid (HNO₂) based on the balanced equation:
The molar ratio of nitrous acid to KOH is 1:1.
The reacting moles of HNO₂ are 1/1 × 0.0114 mol = 0.0114 mol
Finally, we calculate the initial concentration of nitrous acid (HNO₂) in the solution:
0.0114 moles of nitrous acid (HNO₂) are in 25.0 mL of solution.
[HNO₂] = 0.0114 mol / 0.0250 L = 0.456 M
Therefore, the original concentration of nitrous acid (HNO₂) in the solution is 0.456 M.