Net Ionic Equations Lab

A one-day, hands-on station lab for Chemistry and Honors Chemistry (Unit 3: Ionic Bonding). Students mix drops of salt solutions on a watch glass, look for evidence of a reaction, and use what they see to write net ionic equations. It is a microscale lab: each reaction uses only a few drops, so seven stations run on very little solution and make very little waste. Plan on about 30 minutes for the stations, which leaves time for cleanup in a 45-minute period.

Lab Photos

Lab Synopsis

Students rotate through seven stations. At each one, they put 3 drops of one solution on a watch glass, add 3 drops of a second solution on top, and watch for a minute. They record what they see: a precipitate, a color change, gas bubbles, or a metal that grows a coating. Most mixtures react right away, including a bright yellow precipitate that always gets a reaction from the class. One pair does nothing at all, and that is the point. It shows students that ions only react when one of the new combinations does not dissolve.

Five stations are double-replacement pairs. The other two are single-replacement reactions: zinc in copper (II) sulfate, where a copper coating slowly forms on the zinc, and magnesium in hydrochloric acid, where hydrogen gas bubbles off right away. Afterward, students use their data to write molecular, complete ionic, and net ionic equations. For the background, see the Net Ionic Equations (Double) and Net Ionic Equations (Single) lessons. For a digital version, try the Net Ionic Reactions Lab (activity).

Skills Students Practice

• Using a pipette to deliver drops without contaminating the solutions
• Making and recording specific, qualitative observations
• Recognizing evidence that a chemical reaction happened
• Recognizing a gas-forming reaction between a metal and an acid
• Using solubility rules to explain which pairs form a precipitate
• Writing molecular, complete ionic, and net ionic equations and identifying spectator ions
• Comparing double-replacement and single-replacement reactions
• Handling and disposing of heavy metal solutions safely

Materials

The teacher preparation guide has the amount of each chemical for 100 mL and 250 mL of solution, a bottle count, a supply list, and waste handling. The answer key has the expected observation and net ionic equation for every station.

Station Setup

Run seven stations, one reaction each, in the same order as the student data table. Groups rotate through all seven.

Station	Solution A	Solution B
1	1 M sodium chloride	0.1 M copper (II) sulfate
2	0.1 M lead (II) nitrate	0.1 M potassium iodide
3	0.1 M silver nitrate	1 M sodium chloride
4	0.1 M copper (II) sulfate	1 M sodium hydroxide
5	Zinc pieces (small cup)	0.1 M copper (II) sulfate
6	0.1 M lead (II) nitrate	1 M sodium chloride
7	Magnesium ribbon pieces (small cup)	1 M hydrochloric acid

Procedure

1. Set a clean, dry watch glass on a sheet of white paper.
2. Use the pipette that goes with the first solution to add 3 drops to the center of the watch glass.
3. Use the pipette that goes with the second solution to add 3 drops right on top of the first drops. Keep the pipette tip above the liquid so it never touches the drops or another solution.
4. Watch for 1 minute. Record the color, cloudiness, and anything that forms. If nothing changes, record “no visible change”.
5. Metal stations (5 and 7): place one small piece of metal in the watch glass and add 5 to 8 drops of solution to cover it. Zinc reacts slowly, so check it every minute for 5 minutes. Magnesium reacts right away, so watch it for 1 minute. The watch glass at station 7 may get warm.
6. Hold the watch glass over the waste beaker and rinse everything, including any metal, into the beaker with the wash bottle. Dry the watch glass with a paper towel.
7. Put each pipette back with its own solution and move to the next station.

Evidence of a reaction: a precipitate (cloudy, milky, or solid bits), a color change, gas bubbles, or a solid metal that changes or grows a coating. Students who see a white or cloudy solid slide black paper under the watch glass to check.

Safety

• Students wear chemical splash goggles and gloves the whole time, including cleanup.
• Nothing goes down the sink. All liquids and solids go in the waste beaker, since several of these chemicals contain heavy metals.
• Keep flames away from station 7. Magnesium and hydrochloric acid make hydrogen gas, which is flammable.
• Never return extra solution to a bottle, and never switch pipettes between bottles.
• Rinse any skin contact with water right away. For eye contact, use the eyewash for 15 minutes. Report every spill.
• No food or drink. Everyone washes their hands with soap before leaving.

Chemical	Main hazards	Handle it safely
Sodium chloride (1 M)	Low hazard. May irritate eyes.	Keep away from eyes.
Copper (II) sulfate (0.1 M)	Harmful if swallowed. Irritates skin and eyes. Toxic to aquatic life.	Avoid skin contact. All waste in the waste beaker.
Lead (II) nitrate (0.1 M)	Toxic if swallowed. May harm an unborn child. Can damage organs with repeated contact. Toxic to aquatic life.	Wear gloves. Never touch your face. All waste in the waste beaker. Wash hands well.
Potassium iodide (0.1 M)	Low hazard. May irritate skin and eyes.	Keep away from eyes.
Silver nitrate (0.1 M)	Can damage eyes. Stains skin dark brown or black, and the stain shows up hours later. Toxic to aquatic life.	Wear gloves. Rinse any contact right away, even if nothing shows yet.
Sodium hydroxide (1 M)	Corrosive. Can burn skin and cause serious eye damage.	Handle with extra care. Rinse any contact with plenty of water.
Hydrochloric acid (1 M)	Corrosive. Irritates skin and can cause serious eye damage.	Handle with extra care. Rinse any contact with plenty of water.
Zinc (solid)	Low hazard as a solid piece.	Rinse it into the waste beaker when done.
Magnesium (ribbon)	Flammable solid. Makes flammable hydrogen gas with acid.	Keep away from flames. Rinse leftover metal into the waste beaker.

Tips for Teachers

• Model one reaction first. Before the stations open, mix copper (II) sulfate and sodium hydroxide under a document camera and write a strong observation together, such as “light blue, jelly-like solid forms right away.” Then “it changed” stops being an acceptable answer.
• Plan around the slow station. The zinc reaction at station 5 needs about 5 minutes. Let groups start it, move on, and come back to check the zinc instead of holding up the rotation.
• Guard against contamination. Use dropper bottles or tape each pipette to its bottle. A stray drop of the wrong solution can make the no-reaction station turn cloudy, and it is the most common cause of confusing data.
• Put black paper at stations 3 and 6. The white precipitates there are easy to miss on white paper.
• Use distilled water everywhere. Chloride in tap water turns silver nitrate and lead (II) nitrate cloudy, both in the stock bottles and in the wash bottles.
• Spend time on the “no” station. Station 1 is the only pair that does not react, and it is where spectator ions make sense. Ask students why every ion stayed dissolved.
• Prep the magnesium. Cut the ribbon into 1 cm pieces, and rub dull ribbon with steel wool so it reacts right away. Keep Bunsen burners off during the lab, since station 7 makes hydrogen gas.
• Keep heavy metals out of the drain. Empty the station waste beakers into one labeled heavy metal waste container at the end of each period, and collect the copper-coated zinc as solid waste.
• Have a plan for absent students. The Net Ionic Reactions Lab (activity) lets them practice the same observation and equation skills online.

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Downloads

• Net Ionic Equations Lab, Student Version (PDF)
• Net Ionic Equations Lab, Teacher Preparation Guide (PDF)
• Net Ionic Equations Lab, Answer Key (PDF)