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The Alkaline Earth and Solubility

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Chemistry 1

The Alkaline Earth and Solubility

Click here to download: The Alkaline Earth and Solubility Lab

Objective

 

The periodic table is arranged in order of increasing atomic number.  The table is arranged so that each column has elements with similar chemical properties.  These physical and chemical properties of the elements in a column change gradually as you go up or down a column.  By observing trends we can organize the elements of a family in the order that they appear on the periodic table.

 

The alkaline earth is all moderately reactive metals and includes barium, berllium, calcium, magnesium, radium, and strontium.  All alkaline earths exist in compounds and solutions as M2+ cations.  If these cations are mixed with solutions containing certain X2- anions, solid salt compounds will be formed.  If a solid is formed in a solution, this solid is said to e insoluble in the solution.  The solid precipitates, in other words, solid falls out of the liquid solution.

 

M2+(aq) + X2-(aq) MX(s)

 

The expectation is that there will be a trend in the solubility’s of the alkaline earth salts, going from one that forms many soluble salts to one that forms many insoluble salts.  By comparing their solubility’s, the order of the alkaline earths on the periodic table will be determined.

 

**Many of the chemicals used in this experiment are poisonous or corrosive (will cause burns).  Skin and eye contact must be minimized.  The yellow solution WILL stain.**

 

 

Procedure 

 

 1) Get 4 small test tubes and label them as Ba, Ca, Mg, and Sr. Wash each test tube with a brush and rinse with distilled water.  Shake out any water drops that are in the test tubes.

2) To the first test tube, add 10 drops of 1 M Ba(NO3)2

    To the second test tube, add 10 drops of 1 M Ca(NO3)2

    To the third test tube, add 10 drops of 1 M Mg(NO3)2

    To the fourth test tube, add 10 drops of 1 M Sr(NO3)2

3) To each of the four test tubes, add 10 drops of 1 M H2SO4

4) Mix each test tube by holding the top of the test tube and tapping the bottom of the test tube. Record your observations in a table, noting whether a precipitate forms and whether there are any other characteristics to distinguish between the four test tubes such as color, tendency for the solid to settle to the bottom, cloudiness or size of the particles.

5) Dump the contents of each test tube into a waste beaker at your bench.  Wash each test tube with a brush and rinse with distilled water.  Shake out any water drops that are in the test tubes.

6) Repeat step #2-5, but instead of adding 10 drops of 1 M H2SO4, add 10 drops of 1M Na2CO3.

7) Repeat step #2-5, but instead of adding 10 drops of 1 M H2SO4, add 10 drops of .25M (NH4)2C2O4.

8) Repeat step #2-5, but instead of adding 10 drops of 1 M H2SO4, add 10 drops of 1M K2CrO4.

9) The next tests will determine an unknown alkaline earth solution. Test one unknown solution (either A, B, C, or D). This unknown is either Ba(NO3)2, Ca(NO3)2, Mg(NO3)2, or Sr(NO3)2.

10) To each of the four test tubes, add 10 drops of the one unknown solution you chose to use. Record the unknown solution.

11) To the first test tube, add 10 drops of 1 M H2SO4

    To the second test tube, add 10 drops of 1 M Na2CO3

    To the third test tube, add 10 drops of .25 M (NH4)2C2O 4

    To the fourth test tube, add 10 drops of 1 M K2CrO4 and 10 drops of 1 M acetic acid

12)Repeat step # 4-5

1 M H2SO4
1 M Na2CO3
.25 (NH4)2C2O4
1 M K2CrO4
1 M acetic acid
1 M Ba(NO3)2
1 M Ca(NO3)2
1M Mg(NO3)2
1 M Sr(NO3)2
Unknown Compound ___

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