Water Hardness NotesWater Hardness Notes

Applied ChemistryApplied Chemistry

Atom UnitAtom Unit

Water HardnessWater Hardness A. Definition: A. Definition: water hardnesswater hardness is a is a

measure of the amount of measure of the amount of salts dissolvedsalts dissolved in water.in water.

– 1. Salts dissolved in water to produce 1. Salts dissolved in water to produce ionsions,, which are charged particles. which are charged particles.

Salts are present in the ground as Salts are present in the ground as mineralsminerals..

Surface water usually contains Surface water usually contains lowlow levels of hard-water ionslevels of hard-water ions..

Water HardnessWater Hardness

Ground water that flows through limestone, Ground water that flows through limestone, dolomite, magnesite, or gypsum dissolve dolomite, magnesite, or gypsum dissolve salts that result in salts that result in highhigh levels of hard-water levels of hard-water ions.ions.

Hard-water ionsHard-water ions include include CaCa+2+2, , MgMg+2+2, or , or FeFe+3+3

Measurement: water is usually Measurement: water is usually tested for tested for CaCa+2+2

Units:Units:– Parts per million Parts per million ppmppm

– 1 milligram per liter = 1 ppm1 milligram per liter = 1 ppm

– Grains per gallonGrains per gallon

– 1 grain/gallon = 1 grain/gallon = 17 ppm17 ppm

MeasurementMeasurement

Range of valuesRange of values– Soft waterSoft water less than 120 ppmless than 120 ppm

– Moderately hard waterModerately hard water 120-350 ppm120-350 ppm

– Very hard waterVery hard water over 350 ppmover 350 ppm

Types of HardnessTypes of Hardness

Temporary hardness is hardness that Temporary hardness is hardness that cancan be removed by boilingbe removed by boiling

Permanent hardness is hardness that Permanent hardness is hardness that cannotcannot be removed by boiling be removed by boiling

Hard Water UseHard Water Use

1. Need more 1. Need more soapsoap for cleaning. for cleaning.

2. Forms 2. Forms scumscum when hard-water ions react when hard-water ions react with soap.with soap.

3. Forms 3. Forms scalescale, a build-up in tea kettles and , a build-up in tea kettles and hot water heaters.hot water heaters.

Treatment of Hard WaterTreatment of Hard Water 1. 1. Water softenersWater softeners are installed within are installed within

your home plumbing.your home plumbing.– These units contain an These units contain an ion exchange resinion exchange resin

which are tiny, insoluble, porous beads.which are tiny, insoluble, porous beads.

– Hard water passes over the ion exchange Hard water passes over the ion exchange resin and the unwanted Caresin and the unwanted Ca+2+2, Mg, Mg+2+2, and Fe, and Fe+3 +3

are exchanged, or traded, for are exchanged, or traded, for NaNa+1+1..

– Health concern: increased levels of Health concern: increased levels of sodium in your diet.sodium in your diet. Solution:Solution: by-pass on kitchen sinkby-pass on kitchen sink