posted by anonymous on .
Write formula equations and net ionic equations for the hydrolysis of the following salts in water.
a. sodium carbonate
b. ammonium bromide
I don't know what the products should be.
a. Na2CO3+H2O--> ?
b. NH4Br+H2O--> ?
Please help me with this. I really need this. Thanks in advance.
The hydrolysis of Na2CO3 ends us as the hydrolysis of the carbonate ion.
The molecular formula is
Na2CO3 + HOH==NaHCO3 + NaOH
NaHCO3 + HOH ==> H2CO3 + NaOH
The net ionic equations are
CO3^= + HOH ==> HCO3^- + OH^-
HCO3^- + HOH ==> H2CO3 + OH^-
but your teacher PROBABLY want you to show how you get from steps 1 and 2 to steps 3 and 4.
For NH4Br + HOH ==> NH3 + HBr
I'll let you make the change to the net ionic equation but I'll give you a hint. The Br^- is not hydrolyzed; the NH4^+ is hydrolyzed.
I don't understand how you come up with this, are there any steps or rules in doing this?
For the NH4Br equation, do you understand the molecular equation I wrote. If so, I can give you the details on how we go from the molecular to the net ionic equation. The carbonate is tougher to explain on the boards like this.
I don't get it....
Hydrolysis of NH4Br means just that. Hydrolysis means to react the compound with water. So we write
NH4Br + HOH ==> and do a double displacement reaction.
NH4Br + HOH ==> NH4OH + HBr.
We know that NH4OH doesn't exist, actually it's NH3 + H2O so let's write it that way.
NH4Br + HOH ==> NH3 + H2O + HBr
These are aqeous solution so we write them as ions. (This is changing the molecular equation into the ionic equation.)
NH4^+ + Br^- + HOH(l) ==> NH3(aq) + H2O(l) + H^+ + Br^-
The next step is to cancel ions common to both sides.
Immediately, I see a Br^- on each side so we cancel them.
NH4^+ + HOH ==> NH3 + H2O + H^+.
The H2O + H^+ combine to make the hydronium ion.
NH4^+ + HOH ==> NH3 + H3O^+
The last one is the net ionic equation.
Can you explain that to me please?
O thanks a lot :)
I think I got it!
But I'm still confused with the sodium carbonate one
Why wouldn't NH4OH exist? Is it because the strength of the Hydroxide dominates the strength of the weak acid: NH4+?