posted by Lisa on .
Predict qualitatively whether the salts below dissolve to give solutions that are acidic, basic or neutral.
what is the rule for figuring this out?
a. KNO2 - basic
b. Ng(NO3)2 - neutral
c. NH4ClO2 - acidic
d. NaHCO3 - basic
I think the difficult way is to try to explain it on the basis of acidic or basic nature of the cation or anion; therefore, I don't think like that.
I write the hydrolysis of the salt (which isn't always correct BUT it gets the right answer) except in some special circumstances.
KNO2 + HOH ==> KOH + HNO2
Now look at the products. KOH is a STRONG base; HNO2 is a WEAK acid; therefore, KNO2 will be basic (from the strong base).
For cases where both the acid and base formed are strong, the salt is neutral.
For cases where both acid and base formed weak, it depends upon which is the stronger and Ka and Kb tables will help you decide. For the extra special case of NaHCO3, I remember (H^+) = sqrt(k1k2) which is about pH 8.3 or so.