Estimate EDTA method of determining hardness of water
Question
Estimate EDTA method of determining hardness of water
Solution
The EDTA method of determining hardness of water involves the following steps:
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Collection of Water Sample: The first step is to collect a sample of the water whose hardness is to be determined.
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Preparation of Buffer Solution: A buffer solution of pH 10 is prepared. This is because the reaction between EDTA and the metal ions in the water is best at this pH level.
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Addition of Indicator: An indicator, such as Eriochrome Black T, is added to the water sample. This indicator forms a wine-red complex with the metal ions in the water.
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Titration with EDTA: The water sample is then titrated with a solution of EDTA. EDTA reacts with the metal ions in the water to form a stable complex. As this reaction occurs, the indicator changes color from wine-red to blue.
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Calculation of Hardness: The volume of EDTA used to reach the endpoint of the titration is noted. This volume is used to calculate the hardness of the water.
The formula used to calculate the hardness of water is:
Hardness (mg/L) = (Volume of EDTA (mL) x Molarity of EDTA x 1000) / Volume of water sample (mL)
This method is widely used because it is relatively simple and accurate. It can be used to determine the total hardness of the water, as well as the individual concentrations of calcium and magnesium ions, which are the primary contributors to water hardness.
Similar Questions
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