Urgent! Need help with salts!! (1 Viewer)

[alexx-12]

Hi everyone,
i have a titration prac test tomorrow and theres going to be questions on salts.
How do we know if a salt is acidic basic or neutral?
do we just have to memorise common acidic and basic salts or is there a way to work it out?

thanks in advance

 

[Da_Bomb]

Yeh just remember these:

Strong base + weak acid --> slightly basic salt
Strong acid + weak base ---> slightly acidic salt
Weak acid + weak base ----> neutral salt
Strong acid + strong base ---> neutral salt

And say if you're just given the name of salt, you can work out whether its acidic, basic or neutral.

For example . NaCl ( sodium chloride)

First of all, the Cl part would come from HCl( hydrochloric acid) which is a strong acid. And then the Na part would come from NaOH (sodium hydroxide) which is a strong base. And looking at the above rules you see that strong base reacts with strong acid to form a neutral salt. Therefore, NaCl is a neutral salt.

 

[hvf26]

yep, remember the rules for the basicity/acidity of salts
conjugate bases from strong acids (HCl, HNO3, H2SO4) do not react
OH does not react
group I and II metals do not react
in addition to what Da Bomb said, when you get the salt just write a quick equation to see if there could be any possible reaction with water to form hydroxide or hydronium ions
example:
1) NH4Cl + H20 <--> NH3 + H30 + Cl
therefore NH4Cl is an acidic salt as it reacts with water to form hydronium ion
2) CaCO3 + H20 <--> Ca + HCO3 + OH
as CaCO3 reacts with water to form HCO3 and hydroxide ion, it is considered a basic salt

 

[alexx-12]

oh ok thanks heaps, thats very helpful
is there a way to work out whether an acid is strong or weak just by being given its name?

 

[Pwnage101]

HCl, HNO3, H2SO4 are all strong, ethanoic (CH3COOH) and citric (C6H8O7) acids are weak. They are the common ones.

 

[hvf26]

HCl, HNO3, H2SO4 are all strong, ethanoic (CH3COOH) and citric (C6H8O7) acids are weak. They are the common ones.

adding onto this, if its not HCl HNO3 or H2SO4, its a weak acid, as only these 3 acids completely ionise in solution