Lab 6- Determination Of Water Hardness

Question 1

Define Hard Water

Answer 1

Water that contains magnesium and/or calcium ions in solution is known as hard water because these ions react with soap to prevent the formation of lather.

Question 2

In what ways can water be “softened?”

Answer 2

Through boiling or through treatment with slaked lime.

Question 3

Define Temporary Hard and Permanent Hard Water

Answer 3

Water that contains at least 2 moles of bicarbonate ions for every magnesium or calcium is called temporary Hard water; if it contains less HCO3-, it is called permanent hard water.

Question 4

In what units is the water hardness usually expressed in?

Answer 4

Parts per million (ppm)

Question 5

What chelating agent will be used in this experiment to determine the hardness of water?

Answer 5

EDTA

Question 6

What indicator will be used in this experiment?

Answer 6

Calmagite

Question 7

How is MgIn- formed and what is its color?

Answer 7

It is formed when Calmagite complexes with magnesium and it has a wine red color.

Question 8

What color of the indicator will signal the endpoint of the titration?

Answer 8

Sky blue.

Question 9

What is the formula for EDTA and Calmagite respectively?

Answer 9

H4Y for EDTA and H3In for Calmagite.