The alkaline earths and the halogens: two families in the periodic table

Introduction: The purpose of this lab was to find the relative solubilities of some salts of the Alkaline Earths and use that information to find the order which they appear in the periodic table; also use that information to efficiently find an unknown alkaline earth halide. Also to find the relative oxidizing powers of the Halogens given and using that information finding the order of the Halogens in the periodic table; also use that information to efficiently find an unknown Halogen.

Experimental Procedure: View pages 25-28 in the lab Manuel.

Data and Observations: Relative Soluabilites of some Salts in Alkaline Earths

| 1 M Na2CO3| 1M H2SO4| 1M (NH4)2C2O4 | 1M K2CrO4 & 1M HC2H3O2| Ca(NO3)2| 1/2 clear, 1/2 Milky| Clear| Milky White| Clear yellow hinge| Ba(NO3)2| Milky White| Milky White| Milky White| Milky Yellow| Mg(NO3)2| 1/2 clear, 1/2 Milky| Clear| Clear| Clear yellow hinge| Sr(NO3)2| Milky White| Milky White solid| Milky White| Clear yellow hinge|

**Unknown #8 reacted with 1M H2SO4 and turned Milky White

Oxidizing ability of halogens

| Cl2(Hexane)| Br2(Hexane)| I2(Hexane)| Cl-| x| | | Br-| | x| | I-| | | x|

**** Unknown #8 reacted with Cl2(hexane) which made

Calculations: Not applicable

Discussion: In part c of the experiment we were asked to list the 4 alkaline earth metals in the order which they should appear in group 2 of the periodic table based on our observations. I came the conclusion that they should appear as (Mg, Ca, Sr, Ba) from top to bottom respectively. I came to this conclusion since I know mass increases from top to bottom of the periodic table and the reactions with more precipitate and color would have a greater mass. So I observed the Relative Soluabilites of some Salts in Alkaline Earths table and saw that Mg had the least precipitate/color, then Ca, then Sr, then Ba had the most.

Also we were asked to find the proper ordering in the periodic table of the given halogens based on our observations. I came to the conclusion that they should appear (Cl, Br, I) from top to bottom respectively. Based on the previous information regarding mass increases as you go down the periodic table I was able to come to this conclusion. I observed that Cl had the least color concentration, then Br, then I had the most. The greater the color concentration, the greater the mass. This observed data let me come to my conclusion.

To find the unknown #8 Alkaline I realized that the only anion that had 4 distinct precipitate reactions for each alkaline was H2SO4, so all I had to do was react Unknown #8 with H2SO4. I did this experiment and the reactant was milky white. Based on this reaction in comparison to my previous reactions I concluded that unknown #8 alkaline was the alkaline earth Ba. This experiment was most efficient because it only took one step to figure out what my unknown was, since their was four different reaction outcomes and four different earth metal each matching to one out come this was clearly the most efficient way.

To find the unknown #8 halide I realized that the Halogen Cl2 had three distinct reactions for each halide. Using this information it made sense to react my unknown #8 halide with Cl2. I did the reaction and the result was a clear mixture which was the same mixture of the Cl2+Cl- reaction. Using this knowledge I came to the conclusion that my unknown #8 halide is Cl-. This experiment is the most efficient since it only entails one step to find the answer, since the halogen Cl2 had 3 distinct reactions with each halide.

Unknown #8= BaCl2

Balanced Equations for All Reactions Observed

Conclusion: I came the conclusion that Alkaline Earths should appear as (Mg, Ca, Sr, Ba) from top to bottom respectively in the periodic table. I also concluded that Halogens should appear (Cl, Br, I) from top to bottom respectively in the periodic table. I also found that Unknown #8= BaCl2.