Experimental Procedure
Part A: Classifying Aqueous Reactions
1. Acquire a clean spot plate.
2. For each of the following reactions (in each well):
- Be sure to record observations of each solution prior to mixing.
- Add 4 -5 drops of the first solution into the designated spot.
- Add 4-5 drops of the second solution into the designated spot (if a solid is needed use a small piece)
- Use a clean toothpick to mix the solutions together.
- Make observations of the mixture from the moment the chemicals are mixed for ~ 2 minutes.
- If you do NOT see evidence of a chemical reaction, use the dropper bottles to touch add 1 drop of each reactant to a piece of pH paper. Then use a toothpick to swirl the reaction mixture and touch the toothpick to the pH paper. If there is a difference then a reaction occurred. Use this as evidence the same way a precipitate or other information would be used to classify reactions.
Pre-Lab Questions
*Students must show their work to receive full credit.
1. What is the net ionic equation for any strong acid reacting with any strong base?
2. In the following reaction, indicate the oxidation numbers for all elements on BOTH sides of the equation. Which element is being oxidized in this reaction. Which element is being reduced in the reaction?
2 Al6 + 6 HCl(aq) → 2AlCl3 (aq) + 3 H2 (g)
3. Students perform a reaction specified in the directions. A precipitate forms. Predict (circle) the precipitate in each of the following cases:
AgNO 3 (aq) + NaCl(aq) → AgCl + NaNO3
HgNO3 (aq) + Na2S(aq)→ HgS + NaNO3
Ba(CH3COO)2 (aq) + NaOH(aq) → Ba(OH)2 + 2 NaCH3COO
Experimental Data and Results
Part A: Classifying Aqueous Reactions
| Well/ Spot | Reactant 1 | Reactant 2 | Reaction Mixture Observations |
|---|---|---|---|
|
Example Observations Before Mixing |
CuNO3 Blue/green aqueous solution. |
Na2S Colorless aqueous solution. |
Solution became cloudy white: Precipitate formed. |
| 1 Observations Before Mixing | HCl | NaOH | |
| 2 Observations Before Mixing | CH3COOH | NaOH | |
| 3 Observations Before Mixing | Na3PO4 | FeCl3 | |
| 4 Observations Before Mixing | (NH4)2CO3 | CuCl2 | |
| 5 Observations Before Mixing | Al (metal foil) | CuCl2 | |
| 6 Observations Before Mixing | CH3COOH | NaHCO3 | |
| 7 Observations Before Mixing | Zn (metal filings) | HCl | |
| 8 Observations Before Mixing | KNO3 | CuSO4 |
Use your observations above, information in the introduction, and reading to classify the above chemical reactions in the table below.
- First: classify the reaction as a main type: either synthesis, decomposition, combustion, single replacement OR double replacement. If no reaction occurred, say N/A. Record your choice in the space provided.
- Second: classify the reaction as an aqueous redox, acid-base, precipitation AND/OR gas evolving reaction. Record your choice in the space provided. Be sure to include all reaction types if there is more than 1.
| Reaction Number | Overall Reaction Type | Aqueous Reaction Type |
|---|---|---|
| Example | Double-Replacement | Precipitation |
| 1 | ||
| 2 | ||
| 3 | ||
| 4 | ||
| 5 | ||
| 6 | ||
| 7 | ||
| 8 |
Post-Lab Questions
- Write the balanced chemical reaction for reaction 1. Be sure to include the states of matter and correct formulas. If applicable (ie: if you classified it as a precipitation reaction) include the net ionic equation as well.
- Write the balanced chemical reaction for reaction 3. Be sure to include the states of matter and correct formulas. If applicable (ie: if you classified it as a precipitation reaction) include the net ionic equation as well.
- Write the balanced chemical reaction for reaction 5. Be sure to include the states of matter and correct formulas. If applicable (ie: if you classified it as a precipitation reaction) include the net ionic equation as well.
- Write the balanced chemical reaction for reaction 7. Be sure to include the states of matter and correct formulas. If applicable (ie: if you classified it as a precipitation reaction) include the net ionic equation as well.