Asked by saddee

A 100.0 mL sample of hard water is titrated with the EDTA solution from Part 2. The same amount of Mg2+ is added as previously, and the volume of EDTA required is 22.44 mL

What volume of EDTA is used in titrating the Ca2+ in the hard water?

How many moles of EDTA are there in that volume?

How many moles of Ca2+ are there in the 100.0 mL volume of water?

If the Ca2+ comes from CaCO3, how many moles of CaCO3 are there in one liter of the water?



How many grams of CaCO3 per liter?

If 1 ppm (part-per-million) CaCO3 = 1 mg per liter, what is the water hardness in ppm CaCO3?



Answers

There are no human answers yet.
Answered by Bot
Let's break down the problem step by step.

1. To find the volume of EDTA used in titrating Ca2+ in the hard water, first determine how much EDTA was used to titrate both Ca2+ and Mg2+:

Volumes of EDTA:
- Total EDTA used for both Ca2+ and Mg2+ = 22.44 mL
- EDTA used for Mg2+ (from Part 2) = 10.11 mL

So, the volume of EDTA used for Ca2+ would be the total volume minus the volume used for Mg2+:

Volume of EDTA for Ca2+ = 22.44 mL - 10.11 mL = 12.33 mL

2. To find the moles of EDTA in the volume used for titrating Ca2+, use the concentration of the EDTA solution from Part 2 (0.00484 M):

Moles of EDTA = (12.33 mL)(0.00484 mol/L) * (1L/1000mL) = 0.000059676 mol (rounded to 3 decimal places)

3. In EDTA titration, the molar ratio between EDTA and Ca2+ is 1:1. So, the moles of Ca2+ in the 100.0 mL volume of water are the same as the moles of EDTA used:

Moles of Ca2+ = 0.000059676 mol

4. If the Ca2+ comes from CaCO3, then the moles of CaCO3 in the water are the same as the moles of Ca2+:

Moles of CaCO3 = 0.000059676 mol (in 100 mL of water)

To find moles of CaCO3 in one liter (1000 mL) of water, multiply by a factor of 10:

Moles of CaCO3 in 1 L of water = 0.000059676 mol * 10 = 0.00059676 mol

5. To find the grams of CaCO3 per liter, use the molar mass of CaCO3 (100.09 g/mol):

Grams of CaCO3/L = (0.00059676 mol)(100.09 g/mol) = 0.059681 g/L

6. Recall that 1 ppm CaCO3 is equal to 1 mg of CaCO3 per liter. To convert grams to milligrams, multiply by 1000:

Water hardness in ppm CaCO3 = 0.059681 g/L * 1000 = 59.681 ppm (rounded to 2 decimal places)

So, the water hardness is approximately 59.68 ppm CaCO3.

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