SC8e Alkalis and Neutralisation Flashcards
What is a neutralisation reaction?
Soluble bases or alkalis react with acids to form a salt and water only.
HCl(aq) →
H+(aq) + Cl-(aq)
NaOH(aq) →
Na+(aq) + OH-(aq)
what actually happens in a neutralisation reaction?
hydrogen ions from the acid react with hydroxide ions from the alkali.
e.g. neutralisation reaction H+(aq) + OH-(aq) →
H2O
how can soluble salts be made?
crystallisation
how can a pure salt be made?
~all of the acid and alkali needs to react so it doesn’t remain and contaminate the solution.
~To make the pure salt, the acid and alkali have to be mixed in the correct proportions.
~This can be done with a titration.
what is a pipette used for?
accurately measure the volume
in a titration reaction how is a acid and alkali used?
acid is added from a burette to a fixed volume of alkali in a conical flask.
how to make a PURE, DRY SOLUBLE SALT
~Carry out a titration
~Write down the exact volume of acid needed to neutralise the alkali
~Use the burette to add the correct volume of acid without the indicator
~Evaporate the water from the solution formed
titration method - shortened using sodium hydroxide and hydrochloric acid
~Use a pipette and pipette filler to add 25 ml of sodium hydroxide to a clean conical flask.
~Add a few drops of phenolphthalein indicator and place the conical flask on a white tile.
~Fill the burette with hydrochloric acid and record the starting volume.
~Slowly open the tap of the burette, and add the acid to the conical flask, swirling to mix.
~Slow the adding of acid when the indicator changes colour.
give a reason why universal indicator is not a good choice for titration and give a example of what is. (2 marks)
No sudden change in colour at end point / gradual colour change difficult to see end point
Methyl orange / phenolphthalein
