Acid-Base Lab (HCl & NaOH)
Add HCl or NaOH to water and watch a live pH meter and indicator colour.
Drag the red HCl bottle or the blue NaOH bottle over the beaker to pour. The colour changes smoothly as the pH moves. The buttons add single drops.
About the Acid-Base Lab (HCl & NaOH)
Free acid-base simulator. Add hydrochloric acid or sodium hydroxide drop by drop to water, watch the pH meter and universal indicator change, and see neutralisation happen. Built for chemistry, the acid-base lab (hcl & naoh) runs instantly in your browser: change a setting or drag an object and the result updates at once, so you learn by trying things out rather than only reading about them.
Add HCl or NaOH to water and watch a live pH meter and indicator colour. Use it to explore chemistry ideas at your own pace, then check what you found against the key ideas further down this page.
How to use the Acid-Base Lab (HCl & NaOH)
- Use the controls to change Concentration of HCl and NaOH. The simulation reacts instantly.
- Pick an option such as 0.01 M, 0.1 M, 1 M to switch modes or load an example.
- Press "+ HCl drop", "+ NaOH drop", "+ 2 mL HCl", "+ 2 mL NaOH" to start, reset or change what is happening.
- Where you see a glowing handle, object, weight or atom, drag it with your mouse or finger. Everything responds in real time.
- Watch the readouts and graphs update as you experiment, and compare what you see with the key ideas below.
Things to try
- Add HCl until the pH reaches 2.
- Then neutralise with NaOH.
- Try the 1 M concentration.
- Watch the pH history graph.
Key ideas you can learn
- Adding a strong acid lowers the pH; adding a strong base raises it.
- Mixing equal moles of HCl and NaOH neutralises to pH 7 (water and salt).
- Because pH is logarithmic, the last drop near neutral changes it the most.
Where this is used in the real world
Neutralisation is used for treating acid spills, antacids, swimming-pool care and wastewater treatment.
Who is this simulation for?
Chemistry students from middle school to university, teachers who need a virtual demonstration, and anyone without access to a lab. It is safe, free and repeatable as many times as you like.
For teachers: project it on the board, let students predict what will happen, then run it together. For students: change one thing at a time and write down what changes.
Frequently asked questions
What happens when HCl reacts with NaOH?
They neutralise each other: HCl + NaOH → NaCl + H₂O. If the moles are equal the solution ends up at pH 7.
Why does pH change so fast near neutral?
With few ions of either kind left, one extra drop makes a big relative change, and pH is a logarithmic scale.
Is the Acid-Base Lab (HCl & NaOH) free to use?
Yes. It is completely free, with no signup, no download and no ads inside the simulation. It runs in your web browser.
Does the Acid-Base Lab (HCl & NaOH) work on a phone or tablet?
Yes. It uses touch as well as the mouse, so you can drag objects with your finger. A larger screen makes the controls easier to see.