What is Acid-Base Neutralization?
Acid-base neutralization is the reaction between an acid and a base to form salt and water. When H+ ions meet OH− ions, they combine and the solution becomes neutral (pH ≈ 7).
In neutralization, acid donates H+ ions and base donates OH− ions. They react: H+ + OH− → H2O. The resulting salt solution can be neutral, slightly acidic, or slightly basic depending on the relative strength of the acid and base.
- •High H+ ions
- •Low OH− ions
- •pH < 7
- •Sour taste
- •Equal H+ and OH−
- •Neutral pH ≈ 7
- •Formed H2O (salt water)
- •Neutral properties
Step-by-step worked examples
50 mL of 0.1 M HCl is neutralized by NaOH. How much NaOH is needed?
HCl + NaOH → NaCl + H2O Moles of HCl = 0.050 L × 0.1 M = 0.005 mol 1:1 molar ratio NaOH needed = 0.005 mol If NaOH is 0.1 M: V = 0.005/0.1 = 0.050 L = 50 mL
Sulfuric acid (H2SO4) neutralized by potassium hydroxide (KOH). Balanced equation?
H2SO4 has 2 H+ ions, KOH has 1 OH− Equation: H2SO4 + 2KOH → K2SO4 + 2H2O 2:1 molar ratio for acid:base
0.02 mol of HNO3 reacts with 0.04 mol NaOH. Which is in excess?
HNO3 + NaOH → NaNO3 + H2O (1:1 ratio) 0.02 mol HNO3 needs 0.02 mol NaOH 0.04 mol NaOH is supplied → 0.02 mol NaOH in excess
Flashcards
Quick quiz
Q1.H+ + OH− → ?
Q2.Neutralization always results in pH =
Q3.Balanced: HCl + Ca(OH)2 →
Q4.Molar ratio in H2SO4 + KOH neutralization?
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Common mistakes
All neutralizations give exactly pH 7. — Correct: The pH depends on the strength of the acid and base; weak-weak pairs may be basic or acidic.
Neutralization means the acid and base are both destroyed. — Correct: The acid's H+ and base's OH− are neutralized, but the salt remains in solution.
1 mole of any acid always needs 1 mole of any base. — Correct: Diprotic acids need 2 moles of monobasic base per mole of acid.
The salt formed has no effect on pH. — Correct: Salts of weak acids/bases can hydrolyze and shift pH.
FAQ
What is the definition of acid-base neutralization?
The reaction between H+ ions (from an acid) and OH− ions (from a base) to form water and a salt, resulting in a neutral or near-neutral solution.
How do you calculate moles needed for neutralization?
Use the balanced chemical equation to find the molar ratio, then: moles of acid × (moles base / moles acid) = moles of base needed.
Can a neutralized solution be acidic or basic?
Yes, if the salt hydrolyzes. For example, ammonium chloride is slightly acidic, and sodium carbonate is slightly basic.
What is an indicator in a neutralization titration?
A substance (like phenolphthalein) that changes color at a specific pH to show when neutralization is complete.