Acid-Base Lab
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flagWhat you'll discover
- arrow_forwardPlace everyday substances on the pH scale from 0 to 14
- arrow_forwardCarry out a virtual titration and read the equivalence point from the pH curve
- arrow_forwardChoose between universal indicator, litmus and phenolphthalein
- arrow_forwardWrite the neutralisation reaction: acid + base → salt + water
The pH scale
Acidity is measured on the pH scale, which runs from 0 (strongly acidic) through 7 (neutral) to 14 (strongly alkaline). It tracks the concentration of hydrogen ions, H⁺: acids release H⁺ in water, while bases release OH⁻ ions that mop H⁺ up.
The scale is logarithmic — each step is a tenfold change. Lemon juice at pH 2 is ten times more acidic than vinegar at pH 3 and a hundred times more than tomato juice at pH 4. Your stomach works near pH 2, your blood holds remarkably steady at 7.4, and soap sits around pH 9 to 10.
Neutralisation
Mix an acid with a base and they destroy each other's character in a neutralisation reaction: acid + base → salt + water. With hydrochloric acid and sodium hydroxide, HCl + NaOH → NaCl + H₂O — the products are simply table salt and water.
At the heart of every neutralisation the same tiny event repeats: H⁺ + OH⁻ → H₂O. Farmers neutralise acidic soil with lime, antacid tablets neutralise excess stomach acid, and toothpaste neutralises the acids made by mouth bacteria. The simulation runs this reaction drop by drop so you can watch the pH respond.
Titration and the equivalence point
Titration is chemistry's precision technique for measuring concentration: add base from a burette, drop by drop, into a measured volume of acid containing an indicator. At first the pH creeps up slowly because plenty of acid remains. Then, near the equivalence point — where moles of base exactly match moles of acid — a single drop sends the pH leaping several units almost vertically.
That steep jump is the signature you will see on the live graph. For a strong acid and strong base the equivalence point sits at pH 7. Past it, extra base accumulates and the curve flattens again in alkaline territory.
Indicators: chemistry you can see
Indicators are dyes that change colour with pH. Universal indicator shows the whole rainbow — red in strong acid, green at neutral, violet in strong alkali — so it estimates pH at a glance. Litmus is simpler: red below 7, blue above, making it a quick acid-or-base test.
Phenolphthalein is the titration specialist: colourless in acid and suddenly pink above about pH 8.3. Because its colour snaps on right where the equivalence jump happens, a single drop of excess base turns the whole flask pink — an unmistakable stop signal. Choose each indicator in the simulation and compare.