Name Date Class

Making Ionic Compounds

Elements combine to form compounds. If energy is released as the compound is formed, the resulting product is more stable than the reacting elements. In this investigation, you will react elements to form two compounds. You will test the compounds to determine several of their properties. Ionic compounds have properties that are different from those of other compounds. You will decide if the products you formed are ionic compounds.

Problem

What are the formulas and names of the products that are formed? Do the properties of these compounds classify them as having ionic bonds?

Objectives

  1. Observe evidence of a chemical reaction.
  2. Acquire and analyze information that will enable you to decide if a compound has an ionic bond.
  3. Classify the products as ionic or not ionic.

Materials

magnesium ribbon

crucible

ring stand and ring

clay triangle

laboratory burner

stirring rod

crucible tongs

centigram balance

100-mL beaker

distilled water

conductivity tester

Safety Precautions

Inline Figure
  1. Always wear safety glasses and a lab apron.
  2. Do not look directly at the burning magnesium. The intensity of the light can damage your eyes.
  3. Avoid handling heated materials until they have cooled.

Pre-Lab

  1. Read the entire CHEMLAB. Identify the variable. List any conditions that must be kept constant.

    Variable: mass of Mg; Constant: there must be an excess of oxygen




  2. Write the electron configuration of the magnesium atom.

    Mg 1s22s22p63s2


    1. Based on this configuration, will magnesium lose or gain electrons to become a magnesium ion?
      lose electrons


    2. Write the electron configuration of the magnesium ion.
      Mg2 + 1s22s22p6


    3. The magnesium ion has an electron configuration like that of which noble gas?
      neon


  3. Repeat question 2 for oxygen and nitrogen.

    0 1s22s22p4, N 1s22s22p3

    a. Both will gain electrons.
    b. 02 - 1s22s22p6, N3 - 1s22s22p3

    c. Both have the configuration of neon.






  4. Use the data table in the next column.
  5. In your data table, which mass values will be measured directly? Which mass values will be calculated?

    The mass of the magnesium and the mass of the magnesium products are calculated. Other mass values are measured directly.




  6. Explain what must be done to calculate each mass value that is not measured directly.

    The mass of magnesium ribbon is calculated by subtracting the mass of the crucible from the mass of the crucible and magnesium. The mass of the magnesium products is calculated by subtracting the mass of the crucible from the mass of the crucible and its contents after heating.




Procedure

  1. Arrange the ring on the ring stand so that it is about 7 cm above the top of the Bunsen burner. Place the clay triangle on the ring.
  2. Measure the mass of the clean, dry crucible, and record the mass in the data table.
  3. Roll 25 cm of magnesium ribbon into a loose ball. Place it in the crucible. Measure the mass of the magnesium and crucible and record this mass in the data table.
  4. Place the crucible on the clay ring. Heat the crucible with a hot flame, being careful to position the crucible near the top of the flame.
  5. When the magnesium metal ignites and begins to burn with a bright white light, immediately turn off the laboratory burner.CAUTION: Do not look directly at the burning magnesium. After the magnesium product and crucible have cooled, measure their mass and record it in the data table.
  6. Place the dry solid product in a small beaker for further testing.
  7. Add 10 mL of distilled water to the dry magnesium product in the beaker and stir. Check the mixture with a conductivity checker, and record your results.

Sample Data

Mass Data
Material(s) Mass (g)
Empty crucible  7.65g
Crucible and Mg ribbon before heating  7.85 g
Magnesium ribbon  0.20 g
Crucible and magnesium products after heating 7.93 g 
Magnesium products  0.28 g

Cleanup and Disposal

  1. Wash out the crucible with water.
  2. Dispose of the product as directed by your teacher.
  3. Return all lab equipment to its proper place.

Analyze and Conclude

  1. Analyzing Data Use the masses in the table to calculate the mass of the magnesium ribbon and the mass of the magnesium product. Record these masses in the table.
  2. Classifying What kind of energy was released by the reaction? What can you conclude about the product of this reaction?

    Heat and light; It is more stable than the reacting elements.



  3. Using Numbers How do you know that the magnesium metal reacts with certain components of the air?

    There is an increase in mass from 0.20 g to 0.28 g.




  4. Predicting Magnesium reacts with both oxygen and nitrogen from the air at the high temperature of the crucible. Predict the binary formulas for both products. Write the names of these two compounds.

    Mg0, magnesium oxide; Mg3n2




  5. Analyzing and Concluding The product formed from magnesium and oxygen is white, and the product formed from magnesium and nitrogen is yellow. From your observations, which compound makes up most of the product?

    MgO; the product appears white.




  6. Analyzing and Concluding Did the magnesium compounds and water conduct an electric current? Do the results indicate whether or not the compounds are ionic?

    Yes; ionic compounds conduct a current in solution.




  7. Error Analysis If the magnesium lost mass instead of gaining mass, what do you think was a possible source of the error?

    Possible answers include that some of the product blew away or that the reaction was incomplete.




Real-World Chemistry

  1. The magnesium ion plays an important role in a person's biochemistry. Research the role of this electrolyte in your physical and mental health. Is magnesium listed as a component in a multivitamin and mineral tablet?

    Answers may include that it is important in nerve impulse transmission. Mg is present in vitamin-mineral tablets.




  2. Research the use of Mg(OH)2in everyday products. What is Mg(OH)2commonly called in over-the-counter drugs?
    Answers might include that it is used in over-the-counter antacids and laxatives, where it is known as milk of magnesia.