Determination of the Hardness of Water from a Waterfall
Experiment # 4a
Title: Determination of the Hardness of Water from a Waterfall
Aim: To determine the molarity of EDTA and to determine the hardness of water by measuring the concentrations of calcium and magnesium in a water sample by titration.
Abstract: The aim of this experiment was to determine the molarity of a sample of EDTA and then to use this sample to determine the hardness of a sample of water. This was done using a titrimetric method. This was standardized using calcium chloride. The calcium chloride was weighed, dissolved and diluted to a known volume. A buffer and indicator were added to the solution which was then titrated with the EDTA. The water sample was then used as the titrating solution and the procedure repeated. The hardness of water was determined and was found to be 9.25 x 104 ppm.
Introduction: The main purpose of this experiment was to determine the hardness of water. This is the expression of the total concentration of magnesium and calcium ions in a water sample. This was used because of the fact that these ions combine with soap molecules in water making it ‘hard’ to get sudsy; consequently the soap will not clean effectively.
When water containing calcium and bicarbonate ions is heated, some carbon dioxide is given off. As a result, the solution becomes less acidic and insoluble calcium carbonate is formed:
Ca2+ (aq) + 2HCO3- (aq) → CaCO3 (s) + H2O (l) +CO2 (g)
Hardness of water is normally expressed as parts per million (ppm) CaCO3 or mg CaCO3/L solution. According to the American Water Works Association, ideal water quality has no more than 80 mg CaCO3/L solution.
The ions involved can be determined by method of titration with EDTA. EDTA (ethylenediaminetetraacetic acid), is a weak acid which can form soluble complexes with magnesium and calcium in its ionized form (so neither of them have free ions in solution). The endpoint of the titration can be determined using Eriochrome Black T which initially forms a complex
Title: Determination of the Hardness of Water from a Waterfall
Aim: To determine the molarity of EDTA and to determine the hardness of water by measuring the concentrations of calcium and magnesium in a water sample by titration.
Abstract: The aim of this experiment was to determine the molarity of a sample of EDTA and then to use this sample to determine the hardness of a sample of water. This was done using a titrimetric method. This was standardized using calcium chloride. The calcium chloride was weighed, dissolved and diluted to a known volume. A buffer and indicator were added to the solution which was then titrated with the EDTA. The water sample was then used as the titrating solution and the procedure repeated. The hardness of water was determined and was found to be 9.25 x 104 ppm.
Introduction: The main purpose of this experiment was to determine the hardness of water. This is the expression of the total concentration of magnesium and calcium ions in a water sample. This was used because of the fact that these ions combine with soap molecules in water making it ‘hard’ to get sudsy; consequently the soap will not clean effectively.
When water containing calcium and bicarbonate ions is heated, some carbon dioxide is given off. As a result, the solution becomes less acidic and insoluble calcium carbonate is formed:
Ca2+ (aq) + 2HCO3- (aq) → CaCO3 (s) + H2O (l) +CO2 (g)
Hardness of water is normally expressed as parts per million (ppm) CaCO3 or mg CaCO3/L solution. According to the American Water Works Association, ideal water quality has no more than 80 mg CaCO3/L solution.
The ions involved can be determined by method of titration with EDTA. EDTA (ethylenediaminetetraacetic acid), is a weak acid which can form soluble complexes with magnesium and calcium in its ionized form (so neither of them have free ions in solution). The endpoint of the titration can be determined using Eriochrome Black T which initially forms a complex
References: Johnson R., Taylor E., Analytical Chemistry Laboratory Manual Brown J., et al (2009) Chemistry :The Central Science (11th) Prentice Hall, New Jersey Retrieved from http://www.cle.mnscu.edu/kscott/chem1425/wqlabs/Test14/TotalHardness.pdf on October 6, 2011 Retrieved from http://classes.uleth.ca/200103/chem24101/Expt6.pdf on October 6, 2011 Retrieved from http://www.chem.utk.edu/~chem319/Experiments/Exp6.pdf on October 6, 2011 Post-lab Questions: