Ionic or Covalent?
Chemical compounds are combinations of atoms held together by chemical bonds. These chemical bonds are of two basic types – Ionic and Covalent. Ionic bonds result when one or more electrons from one atom or group of atoms are transferred to another atom. Positive and negative ions are created through the transfer. In covalent compounds no electrons are transferred, instead electrons are shared by the bonded atoms.
The physical properties of a substance, such as melting point, solubility and conductivity can be used to predict the type of bond that binds the atoms of the compound. In this experiment, you will test some compounds to determine these properties. Your compiled data will enable you to classify the substances either ionic or covalent compounds.
Ionic compounds have the following properties:
- a) Crystalline solids (made of ions)
- b) High melting and boiling points
- c) Conduct electricity when molten or dissolved in water.
- d) Many of them are soluble in water but not in a NON POLAR solvents like cyclohexane or acetone.
Covalent compounds have the following properties:
- a) Gases, liquids or solids (made of molecules)
- b) Low melting and boiling points
- c) Do not conduct electricity when dissolved in water.
- d) If the molecule is non polar, it will dissolve only in non-polar solvents like cyclohexane or acetone.
- Compare the melting point of the solids
- Determine the solubility of the solids in water and in acetone.
- Determine the conductivity of aqueous solutions of the soluble solids
- Classify the compounds into groups of ionic and covalent compounds
- Summarize the properties of each group
- List the materials used in this lab. Include the chemicals below:
Chemicals: BE CAREFUL – SOME YEARS I CHANGE THE CHEMICALS DUE TO STOCK – VERIFY THE LIST OF CHEMICALS IS THE SAME BEFORE BEGINNING
- C6H12O6 – Dextrose
- CuCl2•2H2O – Copper (II) Chloride dihydrate
- Na2CO3 – Sodium Carbonate
- C10H8 – Naphthalene
- KI – Potassium iodide
- C6H8O7 – Citric Acid
- NaCl – Sodium chloride
- C12H22O11 – Sucrose
- CuSO4•5H2O – Copper(II) sulfate pentahydrate.
- MgSO4•10H2O (Magnesium Sulfate decahydrate)
- PART 1 – MELTING POINT ORDER
- Before you begin, write a brief description or each substance analyzed
- Make a mold using the aluminum foil to resemble the spot plate so the chemicals do not get mixed up when melting.
- Place a few crystals of each compound in each compartment (Be sure you make a map so you are sure which place belongs to each chemical.
- Draw the lab setup and label a diagram that shows the position of each compound BESIDES the lab setup graph.
- For this experiment, it is not necessary to have the exact values for the melting point. The foil will continue to get hotter as it is heated, so the order of melting will give relative melting points. Note the substance that melts first with a number 1 in data table. Record the order of melting for the other substances.
- After 2 min, record and NOT in table if the substance did not melt. Allow the substances to cool down until you finish the lab. Before leaving, wait for your teacher’s instructions on how to dispose the chemicals.
PART 2: Solubility in water
- Put a few crystals of each of the solids in each well of the spot plate (micro-plate). Add 10 drops of distilled water to each well. Do not stir. Record the solubility of each substance in table 1
PART 3: Conductivity of the aqueous solutions
- Test the conductivity of aqueous solutions by dipping both electrodes into each well of the spot plate. Be sure to rinse the electrodes and dry them with a paper towel after each test. If the bulb of the conductivity apparatus light up, the solution conducts electricity. Record your results in table
PART 4: Solubility in Acetone
- Put a few crystals of each of the solids in each well of the spot plate. Add 10 drops of acetone to each well and record the solubility of each substance in table
Follow your teacher’s instructions for the cleaning and disposal procedures.
Before performing the titration you will build up a table where you will record the initial, final and Δ (difference) in volume. USE RULER TO BUILD THE TABLE. Include units in your table. Show this data table to your teacher for her approval before beginning.
- Classify the substances used in IONIC or COVALENT
- Define the following terms:
- Research and define
- Strong electrolyte, weak electrolyte, and non-electrolyte and give one example of each.
- Write the Lewis structure for all the ionic compounds
- Draw the displayed formula for all the covalent compounds.
- Define the following terms
- Ionic substance
- polar substance
- nonpolar substance
- Predict whether the following compounds are ionic, polar covalent, or nonpolar. a. Na2SO4 _______ b. Acetone, CH3 CO CH3 ________ c. NaC2H3O2 _______ d. Gasoline _______ e. Methanol, CH3OH _______ f. Carbon tetrachloride ________
- Write three characteristics of the ionic compounds
- Write three characteristics of the covalent compounds