Water Module: Session 5. Hard Water

 

What is meant by hard water and why does degree of hardness matter?

 

            Why is ground water typically harder then surface water?

 

 

 

            What happens to soap in hard water?

                                    Wash cloths in rain water

 

 

 

            Why would you want EDTA added to your laundry soap?

 

                        Nitrilotriacetic acid                    sodium tripolyphosphate

 

 

 

            How is hardness determined and expressed quantitatively?

 

                        Estimate by seeing how much standard soap solution is required to produce suds with a given volume of water.

 

                        EDTA titration

                                    Total hardness – Mg+2 and Ca+2

 

                                    Calcium hardness – done at high pH to ppt Mg+2

 

 

                                    Report hardness as:

 

[Ca+2] mM

[Ca+2] ppm

[Ca+2], as ppm CaCO3

 

 

            What are the advantages/disadvantages of hard water?

 

 

 

A total hardness of 50-100 ppm CaCO3 is considered an appropriate level of hardness