Alkalinity as CaCO3

Alk (mg/L as CaC O_{3}) = 50, 000 t im es (ma t h r m e q / L)

Alkalinity is acid-neutralizing capacity, expressed as mg/L as CaCO3 (EW = 50 g/eq). 1 meq/L = 50 mg/L as CaCO3. Titration to pH 4.5 (total) or 8.3 (phenolphthalein). Important for coagulation, nitrification, and corrosion control.

$Alk$ (mg/L): Alkalinity as CaCO3
$eq/L$: Normality of titratable bases

Step-by-step solved example

Sample uses 12.0 mL of 0.020 N acid to the total-alkalinity end point. Sample volume 100 mL. Alk?

Titration of a water sample — acid-neutralizing capacity as CaCO3.

1. meq in sample
0.020 eq/L × 0.012 L = 0.00024 eq = 0.24 meq.
2. as CaCO3
0.24 meq / 0.10 L × 50 mg/meq = 120 mg/L as CaCO3.

Answer: 120 mg/L as CaCO3

10 practice questions

0/10 correct

1.1 meq/L as CaCO3 equals

2.Total alkalinity end point is near

3.Phenolphthalein alkalinity is to about

4.Nitrification consumes

5.2.0 meq/L is

6.Hardness vs alkalinity: they

7.Softening with lime uses alkalinity to

8.If the sample volume doubles and acid used doubles, Alk

9.CO2 acidity is not alkalinity; adding CO2

10.Units mg/L as CaCO3 let you