n the titration of 25.00 ml of a water sample, it took 20.590 ml of 4.995x10-3 M EDTA solution to reach the endpoint. Complete the questions below:
Calculate the number of moles of EDTA required to titrate the water sample. (enter your answer with 3 significant figures)
0.000103
You are correct.
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The total hardness is due to one or a combination of Ca2+, Mg2+, and Fe2+ in your sample. It is convenient to express this hardness as though it was entirely due to Ca2+. Making this assumption, determine the number of moles of Ca2+ present in the bottled water sample titrated.
To determine the number of moles of Ca2+ in the water sample, we need to calculate the moles of EDTA used in the titration and then use the stoichiometry of the reaction.
Given:
Volume of EDTA solution used = 20.590 ml = 20.590 cm^3
Molarity of EDTA solution = 4.995x10^-3 M
First, let's calculate the moles of EDTA used:
moles of EDTA = volume of EDTA solution used * molarity of EDTA solution
moles of EDTA = 20.590 cm^3 * 4.995x10^-3 mol/cm^3
moles of EDTA = 0.1029 x 10^-3 mol
Since the reaction between Ca2+ and EDTA is 1:1, the moles of Ca2+ present in the water sample will be the same as the moles of EDTA used.
Hence, the number of moles of Ca2+ present in the water sample is 0.103 x 10^-3 mol.
To determine the number of moles of Ca2+ present in the water sample, we need to use the stoichiometry of the reaction between EDTA and Ca2+. The balanced chemical equation for the reaction is:
Ca2+ + EDTA → Ca-EDTA
From the equation, we can see that one mole of Ca2+ reacts with one mole of EDTA to form one mole of Ca-EDTA.
Since 20.590 ml of 4.995x10-3 M EDTA solution was required to titrate the water sample, we can calculate the number of moles of EDTA used:
moles of EDTA = volume of EDTA solution (L) * concentration of EDTA solution (M)
= 20.590 ml * (4.995x10-3 mol/L)
= 0.1029 * 10^-3 mol
Since the stoichiometry of the reaction is 1:1 between Ca2+ and EDTA, the number of moles of Ca2+ present in the water sample is also 0.1029 * 10^-3 mol.
Therefore, the number of moles of Ca2+ present in the water sample titrated is 0.000103 mol.