Design and perform an experiment to test the hypothesis that mass is conserved during the chemical reaction. You may use a set-up different from the one shown in Activity 9.2.
To test the hypothesis that mass is conserved during a chemical reaction, we can perform an experiment using a precipitation reaction that does not release gas, such as the reaction between sodium sulfate and barium chloride.
Place two clean, dry conical flasks on a digital weighing balance. Press the tare or reset button to set the reading to zero. Pour the solution of sodium sulfate into one flask and the solution of barium chloride into the other. Keep both flasks on the balance to prevent error caused by solution remaining stuck to the flask walls during transfer. Record the initial reading.
Mix the solutions from both flasks. A chemical reaction occurs, forming a white precipitate of barium sulfate along with sodium chloride. Since no gas is formed, this reaction can be safely carried out in an open system.
After the reaction is complete, record the final reading on the balance. You will observe that the final reading matches the initial reading. This shows that the total mass of the reactants equals the total mass of the products, verifying the Law of Conservation of Mass.
Explanation
The textbook provides the reaction between sodium sulfate and barium chloride as an alternative setup to Activity 9.2. Because this reaction produces a solid precipitate and no gas, it does not require a closed system like a balloon to trap escaping gases. The specific instruction to keep both flasks on the balance during the process prevents measurement errors from solution sticking to the flask walls.
Solution Steps
Step 1: Place two clean, dry conical flasks on a digital weighing balance and press the tare button to set it to zero.
Step 2: Pour sodium sulfate solution into one flask and barium chloride solution into the other, leaving both on the balance, and record the initial mass.
Step 3: Mix the two solutions, allowing them to react and form a white precipitate of barium sulfate and sodium chloride.
Step 4: Record the final mass on the balance and compare it to the initial mass to confirm mass is conserved.