Question 12.3: PREPARATION OF LIQUID CHEMICAL’S STOCK SOLUTION OR CHEMICAL ...
PREPARATION OF LIQUID CHEMICAL’S STOCK SOLUTION OR CHEMICAL FEED SOLUTION USING VOLUMETRIC SOLUTION METHOD
The volumetric solution method is represented by the following formula:
(V_{lc})(C_{lc}) = (V_{ss})(C_{ss}),
where
V_{lc} = volume of bulk liquid chemical solution that must be added to V_{ss} to form stock solution or feed solution
C_{lc} = concentration of bulk liquid chemical solution
V_{ss} = volume of the liquid chemical target stock solution or feed solution
C_{ss} = concentration of liquid chemical’s target stock solution or feed solution
The units of V_{lc} and V_{ss} should be identical, while the units of C_{lc} and C_{ss} should be identical.
Assume a 0.2% (2,000 mg/L) alum stock solution is desired, so every mL of stock solution added to a 2-L jar test unit equals 1 mg/L chemical feed dosage. Also assume that the commercial liquid alum available has a sp. gr. of 1.3303 g/mL, and a concentration of 5.34 lb/gal (640.94 g/L). Determine the volume of liquid alum required to produce one liter of 0.2% alum stock solution, using the volume solution method.
1 (US Customary System):
1 mg∕L = 8.345 lb∕MG = 8.345 × 10^{−6} lb∕gal
(V_{lc})(C_{lc}) = (V_{ss})(C_{ss})
(V_{lc})(5.34 lb∕gal) = (1 L)(2,000 × 8.345 × 10^{−6} lb∕gal)
V_{lc} = 0.00312 L
= 3.12 mL
Therefore, the 0.2% alum stock solution is made up by placing 3.12 mL of liquid alum into a 1,000-mL flask and filling the flask with water to the 1,000-mL mark.
2 (SI System):
(V_{lc})(C_{lc}) = (V_{ss})(C_{ss})
(V_{lc})(640.94 g∕L) = (1 L)(2 g∕L)
V_{lc} = 0.00312 L
= 3.12 mL
Therefore, the 0.2% alum stock solution is made up by placing 3.12 mL of liquid alum into a 1,000-mL flask and filling the flask with water to the 1,000-mL mark.