Two underlying “needs” of the natural world are stability and electrical neutrality. Basically, Newton’s first law of motion reminds us that nature will tend to stay as it is unless it is acted upon by some outside net force. Electric charge creates a force and instability is related to an increase in potential energy. Both of these phenomena are likely to cause changes in matter and the changes that take place in nature do so to remove any net outside force and release energy to provide stability. During the last lab you observed some properties and changes of samples of matter. In this lab you will record detailed observations for use in further exploration of chemical bonding and reactions. The compounds used and the information gathered will be used as the basis for your journey through the processes involved in relatively simple ionic bonding, binary ionic compounds, chemical reactions, and balancing chemical equations. This information will also be needed in determining the eight unlabeled solutions during the Chemistry Finale Mini-lab.
1. Write the balanced chemical equations for the double displacement reaction of ammonium hydroxide with lead (II) nitrate.
2. Looking at the formulas for each solution, which solutions do you think will not react with each other? Explain your choices.
3. If you needed to determine if an unlabeled solution were AgNO3 or Pb(NO3)2, what information would you need from this lab?
Reaction template 13 solutions in dropper bottles
Reaction surface Magnifying glass
1. Place the reaction surface (overhead transparency) on top of the reaction template (page with X’s).
2. Draw out the reaction template on your own paper to use for recording your observations. Do not put the X’s in the squares. Instead you should number each square and during the experiment record your basic observations in the squares. You will probably need to write more details of each reaction than can be written in the squares, you should write your detailed observations on another sheet. Just use the numbers for a square to identify it.
3. Have your teacher approve your data table before continuing.
4. You may now obtain the 13 solutions. You should have your apron and safety glasses until you have cleaned up.
5. Follow the instructions on the reaction template so that you combine all 13 solutions in every binary (two at a time) combination. Record as many details about each reaction as you combine the solutions, then go back and look at each column again to see if any other changes may have taken place over time. Please only do one column at a time so as not to waste any materials if you do not finish before the end of class.
6. Have your teacher approve your data before continuing.
7. Dispose of the reaction materials according to your teacher’s instructions. Do not just rinse down the sink!?
Open the file bondlab.doc. Type the answers in red. Save to your period’s folder as bondlab analysis
Part I - Compound formation, formula writing, and compound naming
1. Write the formulas for each of the thirteen solutions used in this lab. Next to each formula write what you think the name of the compound is.
2. Obtain a list of the actual names from your teacher and see how close you are. Do not change what you wrote in #1.
3. Write a set of "rules" that you think may have been used in naming all of these binary compounds. Use your knowledge of element names, types, location on the periodic table, as well as similarities among the 13 formulas.
4. These are binary compounds, how many different "pieces" (ions) would be required for this type of compound?
5. Identify each "piece" of the thirteen compounds used in this lab.
6. Like atoms, compounds are electrically neutral. Based on this fact, what must be true about the electrical charge of the different "pieces"? Identify what you think the actual charges are for each ion listed in #5.
7. What do you think caused these ions to combine and form these compounds?
Class discussion of chemical bonding and stability.
Part II - Chemical reactions and balancing chemical equations
Open your analysis file saved at the end of Part I. Type the answers in red.
1. List all combinations you think resulted in a chemical reaction. Give your reasoning, for each, as to why you believe these were chemical reactions. Suggestion: Use formulas in a table format.
2. List all combinations that you do not think resulted in a chemical reaction. Suggestion: Use formulas in a table format.
3. Which combinations are obvious non-reactions just by looking at the formulas? Why are these so obvious?
4. Write all of the combinations involving lead(II) nitrate which resulted in a chemical reaction. Write the combinations first with formulas, then directly underneath in words. Use the paper provided by your teacher. The OLD YELLOW reaction has been done for you on the chart.
Class Discussion of chemical reactions and balancing equations.
5. Complete each of the lead(II) nitrate chemical equations in formulas and words.
6. Balance the chemical equations from #4, formulas and words.
7. Identify the proper "state" (aq or s) of each of the reactants and products in #5, formulas only. In order to do this you will need a table of ionic compound solubility. aq means aqueous or dissolved in water and s means a solid. In these types of reactions with substances dissolved in water, the solid is a precipitate which does not dissolve in water. Place the aq or s as a subscript following each formula.
8. What type of reaction are all of these reactions?
Final Teacher Checkpoint - Correct balanced equations for all lead(II) nitrate reactions and answer to #8
Final Lab Report - It Turned YELLOW!
a. Write the balanced chemical equations for all reactions involving ammonium hydroxide.
Be sure to include aq or s for each compound.
b. Which solution do you think is the most reactive based on this lab? The least reactive?
Explain each answer.
c. If you needed to determine if an unlabeled solution were AgNO3 or Pb(NO3)2,
which one solution would you add and why?
Write an evaluation of your group’s performance during this lab activity. Specifically address each group member‘s performance of his/her specific job.(1 - 2 paragraph(s)
Write an evaluation of the lab activity itself (1 paragraph).
Please provide specific and useful information, not just, “I liked my group….this was a fun lab….”. Also, remember to include supporting evidence for your evaluation, this is a science class not a daytime talk show.