Complexometric Titration

QUANTITATIVE DETERMINATION OF TOTAL HARDNESS IN DRINKING WATER BY COMPLEXOMETRIC EDTA TITRATION

L. ANINIPOT1 and L. RAZON2

1NATIONAL INSTITUTE OF GEOLOGICAL SCIENCE, COLLEGE OF SCIENCE

2NATIONAL INSTITUTE OF GEOLOGICAL SCIENCE, COLLEGE OF SCIENCE

UNIVERSITY OF THE PHILIPPINES, DILIMAN, QUEZON CITY 1101, PHILIPPINES

DATE SUBMITTED:

DATE PERFORMED: JULY

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ABSTRACT

Some calculations were made after the experiments; the computed concentration of EDTA is 8.39 x 10-3 M, the titer of CaCO3 is 8.40 x 10-1 mgmL, the total hardness of the water sample is 216 ppm, and the relative standard deviation and confidence interval of the total hardness of water sample are 16.22 ppt and 216 ± 8.68, respectively. According to the water hardness scale, the water sample is said to be “hard”, meaning, many divalent ions (Ca2+ and Mg2+ ions in this case) are present in the water sample. It can be stated that many ions are present in the water sample but cannot identify what chemicals caused the water sample to be “hard”.

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INTRODUCTION

METHODOLOGY

RESULTS AND DISCUSSION

According to the calculations made, the concentration of the standard EDTA solution in molarity is 8.39 x 10-3 M. The table below shows that the concentration of EDTA solution was obtained from getting the average of the three concentrations of EDTA in three trials.

Trial | 1 | 2 | 3 |

M EDTA | 8.78 x 10-3 | 8.33 x 10-3 | 8.08 x 10-3 |

Average M EDTA | 8.39 x 10-3 |

Table 1. The average concentration of EDTA computed from the concentrations of EDTA obtained from three trials

The titer of the solution was obtained by multiplying the formula mass of CaCO3 and molar concentration of EDTA solution. The obtained titer of the solution according to the calculation is 8.40 x 10-1 mg CaCO3/mL EDTA solution.

The total hardness is the main unit needed to be computed in order to determine...