Alkaline Earth Metals LabName

Background:

The arrangement of the elements in the periodic table is one of the most important achievements in modern chemistry. The physical and chemical properties of elements change in a regular repeating pattern as you go both across the rows and down the columns of the table. As a result, when elements close to each other in a row or column are compared, they have many of the same properties. However, when elements farther away from each other are compared, they have very unsimilar properties.

The elements in group 2 of the periodic table are known as the alkaline earth metals. Like all members of a group, or family, they have certain properties that change in a regular pattern. One of these properties is the ability to form precipitates, or solids, as a result of a chemical reaction. A precipitate does not dissolve and will settle to the bottom of the liquid.

In this lab, you will compare the abilities of the alkaline earth metals to form precipitates as a result of a chemical reaction.

Materials

White paper grid

Goggles

Dropper bottles of

Magnesium nitrate Mg(NO3)2potassium carbonate K2CO3

Calcium nitrate Ca(NO3)2potassium sulfate K2SO4

Strontium nitrate Sr(NO3)2potassium chromate K2CrO4

Barium nitrate Ba(NO3)2

Procedure

  1. Place 3 drops of potassium carbonate in each square of the grid under the word “carbonate” Place 3 drops of potassium sulfate in each square of the grid under the word “sulfate”. Follow the same procedure using potassium chromate.
  2. Place 3 drops of magnesium nitrate on top of the drops in each of the first row labeled “Mg”. Observe each spot and note if a precipitate is formed and record the results in the data table.
  3. Follow the same procedure for the following rows making sure to record your results in the data table.

Data Table

Reactions of Alkaline Earth Metals with Carbonate, Sulfate and Chromate

Alkaline Earth Metal / Carbonate
CO3 / Sulfate
SO4 / Chromate
CrO4
Magnesium
Mg
Calcium
Ca
Strontium
Sr
Barium
Ba

Conclusions

  1. Was there evidence of a chemical reaction occurring in any of the squares? ______What is the evidence?______
  1. Which alkaline earth metal formed the least number of precipitates?______Which alkaline earth metal formed the greatest number of precipitates?______
  1. What is the relationship between the number of precipitates formed and the location of the element in its family on the periodic table?
  1. If the ability of an alkaline earth metal to form precipitates is an indication of its ability to chemically react with other substances, which is the most reactive element?______least reactive?______
  1. List the alkaline earth elements in order of their chemical reactivity starting with the most reactive______
  1. How does this order compare to their order in the periodic table?
  1. Based on your results, predict which elements in the group one metals would be most reactive.______