Chem 12 homework
Does anyone know how to do these? o.o
Determine if the following solutions are acidic, basic or neutral. Completely justify your answers.
g) NH4H2PO4 (fertilizer)
j) MgO (Phillips Milk of Magnesia)
December 3, 2012
5 Comments • Newest first
[quote=ChewyC]g) Acidic
h) Basic
Reason:
g) It is a conjugate of a weak base (ammonia) and strong acid ( H2SO4) hence it is acidic as its acidity is higher
h) All metal oxides are basic or, metal conjugates are all basic and oxides are neutral (not sure about the oxide one)
edit: where you from? Year 12 already finished for me in Australia
edit 2: Equations - Make them dissociate, NH4H2SO4 -> NH4 + H2SO4 (dissociation)
Hydrolysis - NH4 + H2O <-> NH5+ + OH-
H2SO4 + H2O -> HSO4- + H3O+
As you can see, due to ammonia acting as a weak base (double arrows), in comparison with sulfuric acid acting as a strong acid (one arrow) its acidity over powers its alkalinity (the production of OH- and H3O+ supports that) One thing thats different is that the formula doesnt seem to apply to normal chemistry rules as if its NH4H2SO4 it should normally be NH4H2SO4+, hence that is why i got a NH5+... if it was NH3H2SO4, it would of made sense and so instead of the hydrolysis of NH4 producing hydroxide ions, we have the NH3 as shown... NH3 + H2O <-> NH4+ + OH-, which makes much more sense. Anyway I hope you see what I mean and good luck [/quote]
Ah, it was actually H2PO4 not H2SO4 lol, but thank you for the help on j)
I'm from Vancouver, Canada, so we still have like 6 months left Our curriculum is from September to February (semester 1 of grade 12) and then February to June (semester 2 of grade 12)
@Blackyoshi Was there any other info that the question gave you?
NH4H2PO4 is neutral
[quote=FuGeeLa]You learned about buffers right? Write out the full chem eqn for each solution in a and b. That'll help.[/quote]
he
No, we didn't learn about buffers yet D: I wrote down the Ka for each one:
NH4 + H2O (equilibrium) NH3 + H3O , Ka(NH4) = 5.6x10^-10
H2PO4 + H20 (equilibrium) HPO4 + H3O , Ka (HPO4) = 2.2x10^-13
H2PO4 + H2O (equilibrium) H3PO4 + OH , Ka (H3PO4) = 7.5x10^-3
now I'm not sure what I'm supposed to do next...I don't even know if what I did so far is right lol
You learned about buffers right? Write out the full chem eqn for each solution in a and b. That'll help.