The Acid Tamer

Why it matters

Pink alkali in a flask. Add acid drop by drop and at one exact moment the pink vanishes — the acid and base have cancelled each other into salt and water. Your stomach does this trick every time you take an antacid.

The idea in plain words

Balance check — neutralisation at its simplest.

Predict first

What forms when sodium hydroxide exactly neutralises hydrochloric acid?

NaOH + HCl → NaCl + H₂O. At the end point the solution is neither acidic nor basic — litmus stays put.

• A stronger acid
• Common salt and water — nothing else — correct
• Chlorine gas
• It just dilutes — acid and base can't react

What you do

Add the acid. Watch the indicator lose its pink at the exact moment of neutrality.

Check yourself

A bee sting (acidic) is soothed by baking soda because…

Acid + base → salt + water, on your skin. (Wasp stings are alkaline — those need a weak ACID like vinegar. Know your enemy.)

Phenolphthalein is pink in the flask at the start and colourless at the end. At the end point the solution is…

Phenolphthalein: pink in base, colourless otherwise. The instant the base is exactly used up, pink disappears — the indicator is still there, just reporting neutrality.

Farmers add slaked lime to acidic soil because…

Same chemistry, field-sized: base cancels acid. Neutralisation runs antacids, toothpaste, sting remedies and agriculture.

• baking soda is cold
• a mild base neutralises the acid — correct
• it dries the skin
• it kills the bee's venom cells
• strongly acidic
• still basic
• neutral — correct
• out of indicator
• lime is a fertiliser
• the base neutralises soil acidity so crops grow — correct
• lime makes soil white and reflective
• it kills all soil bacteria