Fun with Formulas Lab

(student version)

Discussion:

Reminders: Ionic vs. Covalent compounds

Other properties of ionic compounds are that they often easily dissolve in water and they typically have high melting points. Also, when they dissolve, they conduct electricity well (electrolytes).

“Binary Compounds” are those compounds that have only two types of elements present.

Prelab

  1. Give an example of a cation and an anion.

In general, compare and contrast (similarity and difference) cations and anions.

  1. When a compound is formed between ions, what must be true about the sum of the ionic charges?
  2. Write the formula of a compound between 2 of the following ions.

A2-, D3-, E2+, G1-

4. Do metals typically form cations or anions? If electrons are negatively charged, and elements are neutral, would metal elements likely lose or gain electrons to form their ion?

Logistics:

For each station (8 total)construct a chart like this:

What was done / Observations
(Answer questions for the station here)

Questions

  1. Your job is to tutor a new student on writing formulas of ionic compounds. Describe in your own words how to write the chemical formula of an ionic compound from two ions.

2. Give an example of each of the following from any station in the lab:

a)Monatomic cation

b)Monatomic anion

c)Polyatomic ion

d)Binary compound

3a) Copy the following table and complete the table by putting the correct formula for each combination in the table.

Br- / S2- / NO3- / PO43-
Li+
Ba2+ / *
Al3+ / *

b) Name the two compounds that are starred.

c) Put an appropriate label for the columns and the rows on your table.

Further Investigation:

Mention questions that came up while doing this lab. Include any experimentation that you could perform.

Conclusion:

Summarize findings making sure to answer questions proposed in the purpose section. Give specific examples from your lab data to support your statement.

Station #1

This compound is made of aluminum and chlorine. Write the formula for this compound.

Which element is the nonmetal in this compound?

Write a formula for a compound made between aluminum and another halogen.

Station #2

Compound A is made from Iron II and the sulfate ion. Write its formula.

What kind of ion is sulfate?

What does the Roman numeral after the “iron” mean?

Compound B is made from iron with a different charge and the sulfate ion. What is its name and formula?

Station #3

Place the plastic sheet over the paper with the 3 X’s. Add a drop of Na2CO3on top of each of the 3 X’s . This is contributing the carbonate ion to the compound that you will make.

Add one drop of each of the three other solutions to a different carbonate drop.

Write the formula for each new compound.

Ag+ + CO32- makes ______

Cu2+ + CO32- makes ______

Fe3+ + CO32- makes ______

Two of these compounds would need a Roman numeral in its name. Write both acceptable names for each compound.

Station #4

Pick up a small piece of copper with the tongs and put it in a match flame for 5 seconds. You have made a black compound on the surface of the metal.

If the formula is CuO, which of the two possible copper ions is in the compound?

Is this a binary compound?

What is the ending of all binary compounds?

Station #5

This is a sample of sodium phosphate. What two ions, with their charges, make up this compound?

Is this a binary compound?

Write the proper formula for this compound.

Station #6

Place a small amount of each substance in a separate test tube.

Fill each test tube halfway with water and stir the tube with the stirring rod or by tapping the tube.

Which is most likely ionic and why?

Station #7

An ionic compound and a soluble covalent compound (like sugar) have been put into solution.

Using the conductivity meter, check to see if each solution conducts electricity. When placed in the solution, the bulbs will light up brightly if the solution conducts. Rinse and dry the meter between solutions.

Which solution contains the ionic compound? Explain how you know.

Station #8

Put a small amount of each compound on two separate areas of a square of aluminum foil.

Place the foil on the hot plate and turn it to medium heat.

As soon as one compound begins to smoke, use the tongs to remove the foil.

Which of the two compounds is ionic and why?