Question

Water Hardness Lab follow up Questions

Trial	Initial EDTA Volume (mL)	Final EDTA Volume (mL)	Total Volume of EDTA Used (mL)
1	8.5	6	2.5
2	5.0	3.0	2.0
3	3.0	0.5	2.3
		Average Volume of EDTA Used (mL):	2.3

Average Volume of EDTA Used (mL)	Concentration Ca2+ Ions Per Liter of Water (mol/L)	Water Hardness (ppm CaCO3)
2.3	0.0023	230

2.Approximately how much calcium would you ingest by drinking six, 8-oz glasses of your local water? Hint: 1 oz (fluid ounce) = 29.57 mL

3.Suppose an air bubble is initially trapped in the tip of the titrator. During the titration, the air bubble is passed from the titrator. Will the hardness of the water be reported as too high, too low, or unchanged as a result? Explain.

4.The endpoint was overshot! This caused the solution to turn instantly blue. How will this error affect the reported hardness of the water, too high or too low? Explain.

5.Why is it important to repeat the titration two additional times? Will this help the data be more precise or accurate? Explain.

5.In this experiment an EDTA titration was performed. Another common type of titration is an acid-base titration. Specifically, a neutralization titration can be used to determine the concentration of a strong acid if it is titrated with a strong base whose concentration is known. This method uses stoichiometry to determine the unknown acid’s concentration.

Let’s say a student had 1.0 M sodium hydroxide (NaOH) and found a solution of sulfuric acid (H₂SO₄) whose label had faded. She took 10.0 mL of the H₂SO₄, added phenolphthalein as an indicator, and titrated the solution. It took 25.8 mL of the NaOH to complete the titration. What was the concentration of the H₂SO₄? The neutralization reaction is below:

H₂SO₄ (aq) + 2 NaOH (aq)   -->    2 H₂O (l) + Na₂SO₄ (aq)

Answer 1