Chemistry of Natural Waters
Chemistry of Natural Waters
Lab Report
Lauren Braas
Thursday November 12, 2009
Chemistry 111
Group members:
Sheila Azutillo
Markeisha Brown
TA:
Darlene Biziak
Introduction
Water is such an important substance needed by all living species for survival.
Freshwater is needed for agriculture, hydroelectric power, and drinking water. The
United States uses 9 X 1011 liters of freshwater everyday.1 Freshwater is not completely pure. Its composition is based on dissolved solutes ranging from gases in the atmosphere to minerals from rocks and soils. The cations Ca2+ and Mg2+ are the most abundant species found in natural waters. These ions come from soluble sedimentary rocks such as limestone, dolomite, and gypsum.2
The presence of these dissolved ions in the water gives it a chemical property that is called water hardness. Water that is hard has a very high concentration of Ca2+ and
Mg2+, as well as other dissolved cations and anions. Likewise, water that has a very low concentration of these ions is said to be soft. The hardness of water can be measured as concentrations in molarity (M), parts per million (ppm) which is also equal to mg/L, and grains per gallon. The accepted ranges of water hardness is as follows:
Soft water - less than 17mg/l
Slightly hard - 17- 60 mg/l
Moderately hard - 60-120 mg/l
Hard -120-180 mg/l
Very hard 180 + mg/l
It is important to study the hardness of water because of the problems it can cause when left untreated. Hard water can cause “scale,” or build-up in plumbing fixtures and water heaters.3 Scale occurs when calcium carbonate, CaCO3 , is deposited as calcite crystals on the inner surfaces of pipes, and evaporator surfaces. This occurs when water with a high
hardness value is evaporated or heated. This buildup can block pipes, make heat transfers in boilers inefficient, and eventually corrode the metal of the pipes. Scale is considered to be the bane of industry because of the expense of replacing
Lab Report
Lauren Braas
Thursday November 12, 2009
Chemistry 111
Group members:
Sheila Azutillo
Markeisha Brown
TA:
Darlene Biziak
Introduction
Water is such an important substance needed by all living species for survival.
Freshwater is needed for agriculture, hydroelectric power, and drinking water. The
United States uses 9 X 1011 liters of freshwater everyday.1 Freshwater is not completely pure. Its composition is based on dissolved solutes ranging from gases in the atmosphere to minerals from rocks and soils. The cations Ca2+ and Mg2+ are the most abundant species found in natural waters. These ions come from soluble sedimentary rocks such as limestone, dolomite, and gypsum.2
The presence of these dissolved ions in the water gives it a chemical property that is called water hardness. Water that is hard has a very high concentration of Ca2+ and
Mg2+, as well as other dissolved cations and anions. Likewise, water that has a very low concentration of these ions is said to be soft. The hardness of water can be measured as concentrations in molarity (M), parts per million (ppm) which is also equal to mg/L, and grains per gallon. The accepted ranges of water hardness is as follows:
Soft water - less than 17mg/l
Slightly hard - 17- 60 mg/l
Moderately hard - 60-120 mg/l
Hard -120-180 mg/l
Very hard 180 + mg/l
It is important to study the hardness of water because of the problems it can cause when left untreated. Hard water can cause “scale,” or build-up in plumbing fixtures and water heaters.3 Scale occurs when calcium carbonate, CaCO3 , is deposited as calcite crystals on the inner surfaces of pipes, and evaporator surfaces. This occurs when water with a high
hardness value is evaporated or heated. This buildup can block pipes, make heat transfers in boilers inefficient, and eventually corrode the metal of the pipes. Scale is considered to be the bane of industry because of the expense of replacing
References: Saddle River, NJ, 2009. 2 PSU Chemtrek; Keiser, Joseph T., Ed.; Prentice Hall: Englewood Cliffs, NJ, 2009. Survey, 2007. Print. Environmental Resources: Harrisburg, PA, 1978 11