Gravimetric Analysis of Metal Carbonate

Gravimetric Analysis of Metal Carbonate

Tamer El-Maghrabi, Lauren

October 3, 2016

Data:

Mass beaker: 136.192 g

Mass beaker + alkali metal carbonate: 137.716 g

Mass alkali metal carbonate: 1.524 g

Mass of two filter papers: .577 g

Mass beaker, filter papers, SrCO3: 138.262 g

Mass SrCO3: 1.493 g

Color of flame: Yellow

Calculations:

1. Calculate the experimental percent of carbonate in the alkali metal carbonate.

1.493g SrCO3 X (1 mol SrCO3 / 147.6g SrCO3) X (1 mol CO3 / 1 mol SrCO3) X 59.98g CO3 / 1 mol CO3 

= .6067g CO3

.6067g / 1.493g X 100 = 40.6 %

1. Calculate the theoretical percent of carbonate in each alkali metal carbonate.

Li2CO3: 6.94 X 2 = 13.88

13.88 + 59.98 = 73.86

59.981 / 73.86 X 100 = 81.21%

        Na2CO3: 22.99 X 2 = 45.98

                45.98 + 59.98 = 105.96

                59.98 / 105.96 X 100 = 56.61 %

        K2CO3: 39.10 X 2 = 78.20

                78.20 + 59.98 = 138.18

                59.98 / 138.18 = 43.41 %

        Rb2CO3: 85.47 X 2 = 170.94

                170.94 + 59.98 = 230.92

                59.98 / 230.92 X100 = 25.97%

1 a)

Show, by calculation, that the addition of 60 mL of .20 M SrCl2 is in excess and that the unknown alkali metal carbonate is the limiting reagent.

SrCl2:

Moles = concentration X Volume

60 mL / 1000 mL = .060 L

Moles = (.20 mol/L) X (.060L)

Moles = .012 mol

Co3 (aq): 1.524g mass of metal carbonate - .9037 g mass of sodium in the metal carbonate = .6203g CO3

        .6203g CO3 X (1 mol CO3 / 59.98g CO3) = .01035 mol CO3

.012 moles Sr X (1 mol CO33 /  1 mol Sr ) = .012 mol CO3

.01035 mol CO3 X ( 1 mol Sr / 1 mol CO3 ) =  .01035 mol Sr

It is assumed that strontium carbonate is insoluble. However, a very small amount of strontium carbonate is soluble in water

1. What is the solubility of strontium carbonate?

Solubility product of SrCO3, Ksp = 5.60e-10

Solubility product Ksp = [Sr+2][Co3-2]

5.60e-10 = s2

s = 2.37e-5 mol/L

Discussion:

1. Calculate the experimental percent of carbonate in the alkali metal carbonate.

By using the experimental mass for 1.493g SrCO3, I used stoichiometry to find the grams of carbonate. I then divided this mass by the original experimental mass and multiplied by 100 to get 40.6 %.

1. Calculate the theoretical percent of carbonate in each alkali metal carbonate.

I found the molecular weight of the alkali metals plus the carbonate. Using this, I divided this mass mass of carbonate by the total. As a result, I got the following for each alkali metal carbonate: