Initial inspection reveals an inconsistent unit (mol/L). Convert the mol/L

concentration of the acid to Eq/L.

0.25 mol

2 Eq

--------X -------- = 0.50 Eq/L

L

mol

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

0.50 Eq/L

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

be made.

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

solution remaining.

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

desired result.

L

0.90 Eq 1000 mEq

90 mL X ---------- X --------X ---------- = 81 mEq

1000 mL

L

Eq

MD0837

7-6

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