Determination of water hardness in an unknown and tap water 25 mL unknown in 100

Question

Determination of water hardness in an unknown and tap water 25 mL unknown in 100 mL flask filled to volume with water Titration solution - edta .9001g , 75 mL water, 5mL NaOH, pour into 500 ml flask and fill to volume with water
Titration amount 24.5 mL flask 1, 20.9 flask 2, 21.7 flask 3
Tap water Titration solution- .9003g, 75 ml water, 5ml NaOH in 250 ml flask and fill to volume with water.
Titration goes into 50 ml of tap water
Titration amounts- 43.2, 44.3 , 46.1
Determine molarity of edta, M ca2+,ppm Ca, and ppm CaCO3
Determine ppm CaCO3 for tap water too.
Determination of water hardness in an unknown and tap water 25 mL unknown in 100 mL flask filled to volume with water Titration solution - edta .9001g , 75 mL water, 5mL NaOH, pour into 500 ml flask and fill to volume with water
Titration amount 24.5 mL flask 1, 20.9 flask 2, 21.7 flask 3
Tap water Titration solution- .9003g, 75 ml water, 5ml NaOH in 250 ml flask and fill to volume with water.
Titration goes into 50 ml of tap water
Titration amounts- 43.2, 44.3 , 46.1
Determine molarity of edta, M ca2+,ppm Ca, and ppm CaCO3
Determine ppm CaCO3 for tap water too.
25 mL unknown in 100 mL flask filled to volume with water Titration solution - edta .9001g , 75 mL water, 5mL NaOH, pour into 500 ml flask and fill to volume with water
Titration amount 24.5 mL flask 1, 20.9 flask 2, 21.7 flask 3
Tap water Titration solution- .9003g, 75 ml water, 5ml NaOH in 250 ml flask and fill to volume with water.
Titration goes into 50 ml of tap water
Titration amounts- 43.2, 44.3 , 46.1
Determine molarity of edta, M ca2+,ppm Ca, and ppm CaCO3
Determine ppm CaCO3 for tap water too.

Explanation / Answer

1. Unknown solution

Mass of EDTA = 0.9001 g

MW of EDTA = 372.44 g/mol

Moles of EDTA = 0.9001 / 372.44 = 0.0024

Volume of Titrant, VEDTA = 500 mL = 0.5 L

Molarity of EDTA, MEDTA = 0.0024 / 0.5 = 0.0048 M

Average titrant volume used for titration, V2 = (24.5 + 20.9 + 21.7)/3 = 22.37

Ca2+ + H2EDTA2- CaEDTA2- + 2H+

1 mole of Ca2+ reacts with 1 mole of H2EDTA2-

Volume of unknown, V1 = 25 mL

Molarity of Ca2+ in unknown, M1 = MEDTA * V2 / V1

= 0.0048 * 22.37 / 25 = 0.0043 M

MW of Ca = 40.078 g/mol

ppm Ca2+ = M1 * MWCa * 1000

= 0.0043 * 40.078 * 1000 = 173.3

MW of CaCO3 = 100.087 g/mol

ppm CaCO3 = M1 * MWCaCO3 * 1000

= 0.0043 * 100.087 * 1000 = 432.8

2. Tap water

Mass of EDTA = 0.9003 g

Moles of EDTA = 0.9003 / 372.44 = 0.0024

Volume of Titrant, VEDTA = 250 mL = 0.25 L

Molarity of EDTA, MEDTA = 0.0024 / 0.25 = 0.0097 M

Average titrant volume used for titration, V2 = (43.2 + 44.3 + 46.1)/3 = 44.53

Volume of tap water, V1 = 50 mL

Molarity of Ca2+ in tap water, M1 = MEDTA * V2 / V1

= 0.0097 * 44.53 / 50 = 0.0086 M

ppm CaCO3 = M1 * MWCaCO3 * 1000

= 0.0086 * 100.087 * 1000 = 862

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