Design a practical task (the instructions, steps and guidelines on how students will go about doing this practical on the topic"masses, moles and concentrations".
Title: Determination of the Concentration of a Solution Using Masses and Moles
Objective: To determine the concentration of a solution by measuring the masses of solute and solvent and calculating the number of moles present.
Materials:
- Balance
- Beaker
- Stirrer
- Graduated cylinder
- Unknown solution (solute)
- Water (solvent)
Procedure:
1. Measure and record the mass of an empty beaker using the balance. This will be used as a reference for later calculations.
2. Pour a known volume of the unknown solution into the beaker using the graduated cylinder.
3. Measure and record the total mass of the beaker and solution.
4. Calculate the mass of the solvent (water) by subtracting the mass of the empty beaker from the total mass of the beaker and solution.
5. Determine the mass of the solute by subtracting the mass of the solvent from the total mass of the beaker and solution.
6. Calculate the number of moles of the solute present using the formula: moles = mass of solute (g) / molar mass of solute (g/mol).
7. Determine the concentration of the solution in mol/L (molarity) by dividing the number of moles of solute by the volume of the solution in liters.
8. Repeat steps 2-7 for additional trials to ensure accuracy and precision.
Guidelines:
- Make sure to calibrate the balance before taking measurements to ensure accuracy.
- Handle the unknown solution with care and avoid spillage.
- Take multiple measurements and calculate the average value for more reliable results.
- Record all measurements and calculations neatly in a lab notebook.
- Ask for assistance from the instructor if you encounter any difficulties or have questions about the procedure.
Conclusion:
After completing the practical task, you should have successfully determined the concentration of the unknown solution using masses and moles. Make sure to discuss your results and any sources of error in your lab report.