salt04 Heat
of neutralisation: Synthesis of three sodium salts
Ask
for an adult! Sodium hydroxide solution and the acids are corrosive.
* Heat a wire to burn
a hole into a cube of foam rubber. This hole has to fit an injection bottle.
Press it into this hole.
* Use a syringe with a blue
marking to fill 1.0 ml of 1M NaOH into the vial.
* Add a drop of phenolphthalein
solution, measure the temperature of the solution.
* Drip 1M HCl to the NaOH
from a syringe carrying a red marking, mix. Continue adding HCl until
the red colour finally disappears. * Measure the temperature once more.
* Repeat this procedure
replacing the HCl solution by solutions of HF and HBr.
Observations:
Right: During neutralisation
of NaOH by HCl the temperature of the solution increased by 5,6°C (20
drops of 1M HCl were needed).
For the neutralisation with
HF solution only 2 drops were necessary and the temperature rose by 8°C.
* Left: After neutralisation
carefully heat the solutions to obtain the salts NaCl, NaF and NaBr.
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modification: 25.10.2001