Initial inspection reveals an inconsistent unit (mol/L). Convert the mol/L
concentration of the acid to Eq/L.
--------X -------- = 0.50 Eq/L
Substitute the information into the problem solving expression.
C1V1 = C2V2
(0.50 Eq/L)(V2) = (1.0 Eq/L)(4.0 mL)
Solve for the unknown quantity.
(1.0 Eq/L)(4.0 mL)
V2 = ------------------ = 8.0 mL
CALCULATING THE REACTING STRENGTH OF A SOLUTION
At times it may be necessary to calculate the reacting strength of a solution in
order to adjust its concentration. For example, potassium acid phthalate (a primary
standard) is often used to prepare secondary standards such as sodium hydroxide. In
order to adjust a dilute NaOH solution to a higher concentration, it is necessary to
determine the reacting strength of the dilute solution so that the proper adjustment can
Example. You are preparing 100 mL of a 1.0 Eq/L NaOH standard solution.
After titrating this solution against KHC8H4O4, you discover that the concentration of the
NaOH solution is actually 0.90 Eq/L. The flask containing the NaOH has 90 mL of
a. How many mEq are left in the flask? Read the problem carefully and
determine the unknown quantity.
Milliequivalents of compound that remain in the flask.
The remaining volume, expressed in liters, times the actual Eq/L
concentration times an appropriate factor for conversion of Eq/L to mEq/L will yield the
0.90 Eq 1000 mEq
90 mL X ---------- X --------X ---------- = 81 mEq