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Acids, Bases, and Salts-Equilibrium

Submitted by vdeathrow1993 on Tue, 02/15/2011 - 18:35

I recently took an acids and Bases Equilibrium test and my teacher lets us correct our questions for half credit.  I have a lot of trouble with this stuff esp. the salts.  For the multiple choice questions we need the right answer and an explanation why it is correct.  If someone could help me with the following that would be great:

1. A 0.10 M solution of which of the following salts is neutral?
a. NH4F
b.NH4NO2
c.NH4CH3COO
d.NH4OCl
e.NH4CN

2. Of the following, which acids are weak acids?
I. HBr
II.HF
III. HNO3
IV. HNO2
V. H2CO3
VI H3AsO4

a. I,II, and III
b.II,IV,V, and VI
c.I,II, and V
d. IV,V, and VI
e. another combination

3.Which salt is produced from a strong acid and a strong base?
a.LiF
b.KBrO
c.NH4NO3
d.NaHCO3
e.NaHSO4

4. Which of the following acid/ base pairs produce neutral salts when they react?
a. HClO4/Ba(OH)2
b.HF/KOH
c.HBr/LiOH
d.Both (a) and (c)
e.All three choices

Thank you for any and all help.  And remember please explain the answer if you can.  Thank you.


The rule is
1) Salts made from a strong acid and strong base form neutral salts in a solution
1) Salts made from a strong acid and weak base form acidic salts in a solution
1) Salts made from a weak acid and strong base form basic salts in a solution
1) Salts made from a weak acid and weak base can form neutral salts in a solution if the acid and base are equally weak. You would need to consider Ka and Kb values

Look up the Ka and Kb values for the various acids and bases. Strong acids and bases are fully ionised and have high Ka values. eg if you start with 0.1M HCl the solution is fully ionised and contains 0.1M H+ and 0.1M Cl-.

First question looks a bit difficult as from memory the base (ammonia solution) is weak but I think the acids are also weak. When I taught we used to say you cannot predict the pH of such as salt.???