Question

Ethylene diamine tetra-acetic acid (EDTA) is a water-soluble compound that readily combines with metals, such as calcium, magnesium, and iron. The molecular formula for EDTA is C10N2O8H16. One EDTA molecule complexes (associates with) one metal atom. A factory produces an aqueous waste that contains 20 mg/L calcium and collects the waste in 44-gallon drums. What mass (g) of EDTA would need to be added to each drum to completely complex all of the calcium in the barrel? (1 gal = 3.785 L)

Answer 1

Answer: The mass of EDTA that would be needed is 24.3 grams.

Step-by-step explanation:

We are given:

Concentration of
`Ca^(2+)` ions = 20 mg/L

Converting this into grams/ Liter, we use the conversion factor:

1 g = 1000 mg

So,
`\Rightarrow (20mg)/(L)* {1g}{1000mg}=0.02g/L`

Now, we need to calculate the mass of calcium present in 44 gallons of drum.

Conversion factor used: 1 gallon = 3.785 L

So, 44 gallons = (44 × 3.785)L = 166.54 L

Calculating the mass of calcium ions in given amount of volume, we get:

In 1L of volume, the mass of calcium ions present are 0.02 g.

Thus, in 166.54 L of volume, the mass of calcium ions present will be =
`(0.02g)/(1L)* 166.54L=3.3308g`

The chemical equation for the reaction of calcium ion with EDTA to form Ca[EDTA] complex follows:

`EDTA+Ca^(2+)\rightarrow Ca[EDTA]`

Molar mass of EDTA = 292.24 g/mol

Molar mass of
`Ca^(2+)` ion = 40 g/mol

By Stoichiometry of the reaction:

40 grams of calcium ions reacts with 292.24 grams of EDTA.

So, 3.3308 grams of calcium ions will react with =
`(292.24g)/(40g)* 3.3308g=24.33g` of EDTA.

Hence, the mass of EDTA that would be needed is 24.3 grams.