Neutralization of Acid and Base

This demonstration shows the neutralization reaction between sodium hydroxide and dilute hydrochloric acid. The acid is added drop by drop to the base while monitoring the change in pH with red litmus paper until the solution reaches neutrality.

1. Pour a measured amount of sodium hydroxide solution into a beaker.
2. Dip a piece of red litmus paper into the solution to confirm it is basic (it will turn blue).
3. Using a dropper, add dilute hydrochloric acid slowly to the sodium hydroxide.
4. After each addition, stir gently and test with fresh litmus paper.
5. Continue adding the acid drop by drop until the litmus paper no longer changes color, indicating the solution has been neutralized.

Neutralisation Reaction of Sodium Hydroxide and Hydrochloric Acid- KClass Plus:

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📄 The “reaction of sodium hydroxide and hydrochloric acid” - MEL Science: https://melscience.com/AU-en/articles/reaction-sodium-hydroxide-hydrochloric-acid/?srsltid=AfmBOopZkbftCcMgEwMiaq0RcP99CU1YOdMrRgaXt_wcUyHIGah59iVo

• Use universal indicator or a pH probe instead of litmus paper to track the exact pH changes.
• Try other acid-base combinations, such as acetic acid with sodium hydroxide.
• Demonstrate the reaction with phenolphthalein as an indicator to show the color change from pink to colorless.
• [Don't do this!] Ensure the solution is completely neutral then taste the salt water produced. Reasons not to do this include:
  • Lab chemicals may contain impurities or contaminants not safe for ingestion
  • Even after neutralization, small amounts of excess acid or base may remain, making the solution harmful.
  • Safer and more accurate methods (indicators, pH probes) exist to test the reaction instead of tasting.

• Wear safety goggles and gloves to protect from splashes.
• Handle hydrochloric acid with care; it is corrosive.
• Avoid contact of sodium hydroxide with skin, as it can cause burns.

• What is the chemical equation for the reaction? (HCl + NaOH → NaCl + H₂O)
• Why is the acid added drop by drop instead of all at once? (To carefully control the neutralization point and avoid adding excess acid.)
• How does litmus paper indicate when neutralization has occurred? (The paper stops changing color, showing the solution is neither acidic nor basic.)
• What would happen if too much acid were added? (The solution would become acidic, and the litmus would remain red.)