The Foundations of Chemistry

Solution

N

_?_ 0.111 NHNO 3

MHNO 3

Because normality is equal to molarity times the number of equivalents per mole of
solute, a solution’s normality is always equal to or greater than its molarity.

Normalitymolarity or NM

EXAMPLE 11-11 Concentration of a Solution

Calculate (a) the molarity and (b) the normality of a solution that contains 9.50 grams of barium
hydroxide in 2000. mL of solution.

Plan

(a) We use the same kind of logic we used in Example 11-10.

(b) Because each mole of Ba(OH) 2 produces 2 moles of OHions, 1 mole of Ba(OH) 2 is 2
equivalents. Thus,

NM or M

Solution

(a) ? 0.0277 MBa(OH) 2

(b) ? 0.0554 NBa(OH) 2

You should now work Exercises 42 through 44.

From the definitions of one equivalent of an acid and of a base, we see that one equiv-
alent of an acid reacts with one equivalent of any base.It is nottrue that one mole of any acid
reacts with one mole of any base in any specific chemical reaction that goes to comple-
tion. As a consequence of the definition of equivalents, 1 eq acid1 eq base. We may
write the following for allacid–base reactions that go to completion.

Number of equivalents of acidnumber of equivalents of base

The product of the volume of a solution, in liters, and its normality is equal to the
number of equivalents of solute contained in the solution. For a solution of an acid,

LacidNacidLacideq acid

eq acid



Lacid

2 eq Ba(OH) 2



1 mol Ba(OH) 2

0.0277 mol Ba(OH) 2



L

eq Ba(OH) 2



L

1 mol Ba (OH) 2



171.36 g Ba(OH) 2

9.50 g Ba(OH) 2



2.00 L

mol Ba(OH) 2



L

N



2 eq/mol

2 eq



mol

no. eq



mol

no. eq



mol

1 eq HNO 3



mol HNO 3

1 mol HNO 3



63.02 g HNO 3

4.202 g HNO 3



0.600 L

eq HNO 3



L

no. eq HNO 3



L

Because each formula unit of Ba(OH) 2

contains two OHions,

1 mol Ba(OH) 2 2 eq Ba(OH) 2

Thus, molarity is one half of normality

for Ba(OH) 2 solutions.

11-4 Equivalent Weights and Normality 413



Remember that the product of volume

and concentration equals the amount

of solute.

The notationis read “is equivalent

to.”