Determination of the Molarity of a solution Derrick Balladin Learning objectives: ● Describe the relationships between volume and amount of solute to concentration. ● Explain how solution color and concentration are related. ● Calculate the concentration of solutions in units of molarity (mol/L). ● Use molarity to calculate the dilution of solutions. ● Compare solubility limits between solutes. Key questions: ● How do you calculate the number of moles? ● What is the mathematical relationship between the number of moles and molarity? Materials: ● Electronic device: computer, smartphone or tablet. ● PhET Molarity simulation: https://phet.colorado.edu/en/simulations/molarity/about Open Exploration: 1. Play with the simulation Molarity for 5 minutes to find out what this sim is about and describe your observations. Collect and analyze evidence: Continue exploring the simulation choose Copper (II) Sulfate (CuSO4) and answer the following questions: 2. What is the colour of Copper (II) Sulfate (CuSO4) solution within the simulation? What is the molarity of the solution at 0.500 mol CuSO4 and 0.5L solution volume? 3. What is the colour of Copper (II) Sulfate (CuSO4) solution within the simulation? What is the molarity of the solution at 0.500 mol CuSO4 and 0.2L solution volume? 4. What is the colour of Copper (II) Sulfate (CuSO4) solution within the simulation? What is the molarity of the solution at 0.0.11 mol CuSO4 and 0.5L solution volume? 5. What is the colour of Copper (II) Sulfate (CuSO4) solution within the simulation? What is the molarity of the solution at 1.000 mol CuSO4 and 1.000L solution volume? Continue exploring the simulation choose Potassium permanganate (KMnO4) and answer the following questions: 6. What is the colour of Potassium permanganate solution within the simulation? What is the molarity of the solution at 0.400 mol KMnO4 and 1.00L solution volume? 7. What is the colour of Potassium permanganate solution within the simulation? What is the molarity of the solution at 0.508 mol KMnO 4 and 1.00L solution volume? Comment on the saturation of the KMnO4 solution 8. What is the colour of Potassium permanganate solution within the simulation? What is the molarity of the solution at 0.960 mol KMnO4 and 1.00L solution volume? Comment on the saturation of the KMnO4 solution 9. The relative formula mass of a compound is calculated by summing the relative atomic mass values for all the atoms in its formula as shown in the Periodic Table. What is the relative formula of CuSO4 (Cu = 63.55 a.m.u.; S = 32 a.m.u.; and O = 16 a.m.u.) 10. This equation shows how relative formula mass, number of moles and mass are related: number of moles = mass ÷ relative formula mass The triangle diagram may help you with this. Calculate the number of moles of CuSO4 in 318 g CuSO4 11. This equation shows how number of moles; Volume (in L) and Molarity are related: Molarity = moles solute/Liter solution https://www.google.com/url?sa=i&url=http%3A%2F%2Fmrsaintsscience.weebly.com%2Fchapter-14--solutions. Calculate the Molarity of 2 moles CuSO4 in 1 L of water. Conclusions Answer the next questions individually. 11. What happens to the Molarity if the same number of moles are used, but the volume is reduced by half? 12. What is the molarity of glucose in 1L water? The molar mass of glucose is 180.16 grams/mole. The molarity of the glucose solution is equal to the moles of glucose per liter of the solution. 13. The importance of molarity: Chemical solutions are made of a specific chemical (the solute) added to a solution. Molarity is the ration used to express the concentration of this solution. Knowing the molarity of the solution is important because classify the solution as diluted or concentrated (relative to each other), but also the actual concentration. Rank the following CuSO4 solutions, based on the stated molarity. (Lowest ranked as 1: and the highest as 5) Solution A CuSO4 = 0.5M; Solution B CuSO4 = 0.05M; Solution C CuSO4 = 0.25M; Solution D CuSO4 = 1.5M; Solution E CuSO4 = 0.5M; 14. Is concentration the same as molarity? Concentration is expressed as g/L of Kg/L, is the ratio of the amount of solute per amount of solution. Molarity relates the amount of moles of a solute per liter of solution 15. For class discussions: a) Two solutions of an organic substance are mixed in the following manner. 400 mL of 1 M first solution + 500 mL of 2 M second solution. What is the molarity of this final mixture? 1) 1.25 M 2) 1.34 M 3) 1.55 M 4) 2.50 M b) What is the final molarity of a 20ml (V1), 2M (M1) aqueous sodium chloride solution, when 200ml of water is added? Note: final volume (V2) = 20 +200 =220ml M1 x V1 (initial solution) = M2 x V2 (final solution) M2 is unknown After answering, please share your ideas with your group.
