Quick answer: A net ionic equation shows only the species that change, leaving out spectator ions. This AP Chemistry lab on net ionic equation gives the aim, the equipment, the safety points, a step-by-step method, sample results and 8 analysis questions; the answers are on a separate page and the lab sheet is a free printable PDF.
When two solutions react to form a solid, the amount of solid depends on whichever reactant runs out first. In this lab you add increasing volumes of sodium carbonate to a fixed volume of calcium chloride, collect the calcium carbonate and see how the mass changes. The graph reveals the limiting reagent and checks the mole ratio in the equation.
Level: AP Chemistry · Curriculum: AP Chem Unit 4
Aim
To find how the mass of calcium carbonate formed depends on the volume of sodium carbonate added, and to locate the limiting reagent.
Equipment
- 0.400 mol/L calcium chloride solution, 25.0 mL for each trial
- 0.300 mol/L sodium carbonate solution (10, 20, 30, 40 and 50 mL)
- five 250 mL beakers, two measuring cylinders
- funnels, filter papers, balance (0.01 g)
- drying oven or warm shelf, distilled water in a wash bottle
Safety
Wear goggles. Sodium carbonate solution is mildly alkaline and can irritate skin and eyes; rinse splashes with plenty of water. Handle hot filter papers with tongs.
Method
- Weigh five dry filter papers and label them in pencil.
- Add 25.0 mL of calcium chloride to each beaker.
- Add 10, 20, 30, 40 and 50 mL of sodium carbonate to the beakers and stir for one minute.
- Filter each mixture through its paper and wash the precipitate with a little distilled water.
- Dry the papers overnight at about 80 °C or on a warm shelf, then weigh each paper with its precipitate.
- Subtract the paper mass to get the mass of CaCO₃.
Results
Sample data for the mass of dry CaCO₃:
| Volume Na₂CO₃ (mL) | Mass CaCO₃ (g) |
|---|---|
| 10.0 | 0.29 |
| 20.0 | 0.58 |
| 30.0 | 0.87 |
| 40.0 | 0.97 |
| 50.0 | 0.97 |
Analysis questions
Question 1 Equations
Write the balanced molecular equation and the net ionic equation.Question 2 Amounts
Calculate the amount of Ca²⁺ in 25.0 mL of 0.400 M CaCl₂ and the amount of CO₃²⁻ in 10.0 mL and 40.0 mL of 0.300 M Na₂CO₃.Question 3 Limiting reagent
State the limiting reagent for the 10.0 mL and the 40.0 mL trials.Question 4 Theoretical mass
Calculate the theoretical mass of CaCO₃ (100.09 g/mol) for the 20.0 mL and 50.0 mL trials.Question 5 Percent yield
Calculate the percent yield for the 20.0 mL trial and comment on the five yields.Question 6 Graph
Describe the shape of the graph of mass against volume and find the volume at which the lines meet.Question 7 Explain the plateau
Explain why the mass stops rising after 33.3 mL.Question 8 Improve the method
State two errors and how to reduce each.
