Heating curve of water lab answer key

Title: Determination of Water Hardness Using a Titrator

Purpose: Define soft and hard water in order to determine how CaCO3 affects water hardness and how to measure it.

Procedure: I performed an EDTA/EBT titration on a local water supply and was able to measure the water hardness. I then calculated the concentration of Ca2+ ions that were present in the local water supply sample.

Data Tables:

EDTA Titration Volume

Initial EDTA Volume (mL)

Final EDTA Wolume (mL)

Total volume of EDTA use (mL)

Trial 1

10 mL

7.5mL

2.5mL

Trial 2

11 mL

6.5mL

4.5mL

Trial 3

13mL

10mL

3mL

Average Volume of EDTA Used (mL): 3.33mL

Water Hardness

Average Volume of EDTA used (mL)

Concentration of CA2+ ions per liter of water (mol/L)

Water Hardness (ppm CaCO3)

3.33mL

0.00333 mol/L

333.2 ppm

Questions:

A. Because our calculations came out to 333.2ppm for the water hardness I would classify the water as very hard. Anything above 180 ppm is very hard water.

B. 8oz x 8 oz =64 oz x 29.57mL= 1892mL=1.9Lx333.2mg/L=632.7mg

C. 1Lx333mg/L=333mgCa/1150mgCa=.289 x 100=28.9%

Conclusion: I can now tell the difference between soft and hard water and that the minerals present in a water supply are what cause them to be hard or soft. I am also now familiar with a titrator and EDTA/EBT solutions.

Lab Discussion With Partners: I didn’t realize that there were 4 different levels associated with water hardness. We talked about the ways that we could potentially physically identify hard water while we were completing the lab. Hard water just feels like it has slime on you and when you are washing your hands it feels like the soap will never come off. It just feels slimy.