Question

Using Table 7.3, order the following bases from strongest to weakest.

NO₃^-, H₂O, NH₃, and C₅H₅N.

Short answer

Order of basic Strength from Strongest to weakest is

NH₃> C₅H₅N > H₂O > NO₃^-

Step-by-step solution

Strong Bases

A strong base is a base which can easily give [OH^-] ions and take [H⁺] ions from an acid in an acid–base reaction. The examples of strong bases are the hydroxides of alkali metals and alkaline earth metals, like KOH, NaOH and Ca(OH)₂ etc.

Bases strength is given by K_b (base dissociation constant) values, stronger the K_b value stronger will be the base.

Checking Strength

HNO₃ is strong acid hence, its conjugate base will be the weak base, water is also a weak base but stronger than conjugate base of strong acid.

So, NO₃^- <H₂O

Pyridine and NH₃ both are basic due to the presence of lone pair on nitrogen

K_b values of these two are given in the table 7.3 are

Base	Formula	Kb
Ammonia	NH3	1.8×10-5
Pyridine	C5H5N	1.7×10-9

From the table we can say that, C₅H₅N <NH₃

So, the overall order of basic Strength is

NH₃> C₅H₅N > H₂O > NO₃^-