Titration Salt Making Procedures

Salt making is by far my favourite topic in chemistry. For any salt making procedures, we need to know the following information.
a)The reactants you are using to produce them,
b)The chemical equation,
c)Write up steps to produce the salt.

This blog entry is for titration, hence the first thing to decide is the reactants needed reaction.
A) Reactants
i)An Acid - Well you know the usual.
ii)An Alkali - To identify an alkalis, they are any group 1 hydroxides, ammonium hydroxides and calcium hydroxide.

That's all.
Let's take this salt as an example, sodium sulfate.
As the name of the salt suggest, the sulfate part comes from the acid used and the sodium part comes from the alkali.
Logically these are the reactants,
Acid - sulfuric acid (since the salt is a sulfate)
Alkali - sodium hydroxide (since the salt is a sodium substance)

So there is it, the reactants.
Next the chemical equation.
Since Alkali + Acid -------> Salt + Water
We will have this word equation
Sodium hydroxide + sulfuric acid --------> Sodium sulfate + water
2NaOH(aq) + H2SO4(aq) ------> Na2SO4(aq) + 2H2O(l)

Last part is the write up. This is the template we can use.
1. Pipette 25 cm3 of acid into a conical flask. Add 2-3 drops of a suitable indicator.
2. Add alkali from a burette gradually until the indicator changes colour. Note the volume of the alkali needed to neutralise the acid.
3. Repeat the titration by adding this volume of alkali to another 25 cm3 of acid.
4. Evaporate the salt solution until it becomes saturated.
5. Filter the crystals and dry between filter paper.

So in our answer we change the keywords to fit our reagents, so this is how our eassay would look like. Of course the eassay will not be in point form, i put it this way to aid understanding. The keywords that i changed are in red.
1. Pipette 25 cm3 of sulfuric acid into a conical flask. Add 2-3 drops of a suitable indicator.
2. Add sodium hydroxide from a burette gradually until the indicator changes colour. Note the volume of the sodium hydroxide needed to neutralise the sulfuric acid.
3. Repeat the titration by adding this volume of sodium hydroxide to another 25 cm3 of sulfuric acid.
4. Evaporate the sodium sulfate solution until it becomes saturated.
5. Filter the sodium sulfate crystals formed and dry between filter paper.

There you go, this method is salt making for titration.

Enjoy!
Entry by
Json Lim
http://www.oleveltuition.com/

Salt Making - Selection of Method

There are a total of 3 salt making techniques that we need to master for O levels. The 3 methods are,
a)Titration
b)Precipitation
c)Acid Reactions (In my tuition class, we call this excess reagent method)

The selection technique is very simple. Simply ask yourself if the salt is soluble. This should ALWAYS be the first thing you ask yourself.

If the salt is soluble, use either titration or acid reactions.
For titration, it is for salts that contain the following ions: Group 1 ions and Ammonium ion.
E.g. sodium chloride, potassium nitrate, ammonium sulfate, lithium ethanoate.

For acid reactions, it is for all other salts that are soluble.
E.g. copper (II) sulfate, magnesium chloride, barium nitrate, silver nitrate.
That's all for the selection technique for soluble salts.

If the salt is insoluble, use precipitation. That's the only method.
E.g. barium sulfate, lead (II) sulfate, lead(II) chloride, silver chloride, calcium sulfate. Notice no nitrate salts here since all nitrates are soluble.



Enjoy!
Entry by
Json Lim
http://www.oleveltuition.com/