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The Acid test
NO HEATING INVOLVED - EVERYDAY ACIDS AND ALKALIS.
EYE PROTECTION ADVISED
You will need:
- Some cabbage juice indicator
- A 30cm ruler
- a pencil
- 3 x 100ml beakers, yoghurt pots or similar
- A 1p coin
- dropping pipette or syringe with measurements
- some kind of measuring cup /beaker (up to 100ml)
- 200ml boiled ( or distilled) water **
- Bicarbonate of soda (aka sodium bicarbonate)
- 20ml Vinegar ( white is best)
- If no vinegar the juice of a lemon will do
** Note to PARENTS:
The boiled water should be prepared in advance with adult supervision. Boil about 300ml of tap water - for 5 - 10 minutes. You should see white solid ( limescale ) appear after a while. When you think no more white solid is forming - let the water cool before filtering/decanting . Allow to cool for later use.
This is what we did!
Diluting the vinegar
- Dilute your vinegar by adding 10ml of vinegar to 90 ml (boiled) water.
- Add 10ml of this solution to a clean beaker
- Add enough cabbage juice extract to give a strong colour.
- Add a similar amount of cabbage juice to another clean beaker with just (boiled) water in it.
Neutralising the acid
- Use a pipette or syringe to add small volumes ( note how much each time) of the sodium hydrogen carbonate solution to the diluted vinegar.
- As you add it, the colour of the cabbage juice will change from red to a blue colour.
- Your task is to find the volume of sodium hydrogen carbonate solution needed to change the colour to a blue colour ( the same as the colour when in water).
This is what we found out
The tekkie bit..
In this experiment we made a solution of sodium bicarbonate ( sodium hydrogen carbonate) .
Sodium hydrogen carbonate has the following chemical formula:
I added 72ml of vinegar diluted to make it a light reddish colour. Then I added 40ml of sodium hydrogen bicarbonate and it looked the same as it did before.