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Dilution of Solutions

Dilution of Solutions. Dilution of Solutions. add water concentrated dilute acid acid MOLES ARE THE SAME.

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Dilution of Solutions

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  1. Dilution of Solutions

  2. Dilution of Solutions add water concentrated dilute acid acid MOLES ARE THE SAME Dilution is the process of decreasing the concentration of a solution by adding more solvent. This does not change the amount of solute, just its concentration.

  3. Concentrated sulphuric acid has a concentration of 18 mol/L. What volume should be used to prepare 2.00 L of 1.00 mol/L sulphuric acid? Step 1: Using what is given, calculate the number of moles of the dilute solution. nD= cDVD = (1.00 mol/L)(2.00L) = 2.00 mol n c V

  4. Step 2: Remember the number of moles are the same in both the concentrated and the diluted solution. nD = nC = 2.00 mol

  5. Step 3: Use the number of moles from the dilute solution to calculate the volume of the concentrated acid required. vC = = =0.11L The volume of concentrated acid required is 0.11 L nC cC 2.00 mol 18 mol/L

  6. Step 4: Calculate how much water was needed to make this solution Vwater= volume of solution – volume of acid = 2.00 L – 0.11 L = 1.89 L To make this solution, add 0.11 L concentrated acid and 1.89 L of water.

  7. Because the number of moles will not change, we can use the formula: CiVi=CfVf Ci =initial concentration of the solution Vi= initial volume of the solution Cf= final concentration of the solution Vf= final volume of the solution

  8. For a chemistry lab, you need a 2.0L of 0.10 M of H2SO4. This acid is usually sold as 18 M. How much initial concentrated acid was used to make the 2.0L acid diluted in water? How much water was added in the dilution? Ci =18M Vi= ? L Cf= 0.1M Vf= 2.0L CiVi=CfVf Vi=CfVf Ci Vi=(0.10M)(2.0L) / 18M = 0.01L Vf-Vi= 2.0L – 0.01L= 1.99L of water was added

  9. Herman has to dilute a 2.0mol/L copper (II) sulfate solution with a volume of 0.63L to make a 250mL solution. What is the final concentration? Ci =2.0M Vi= 0.63 L Cf= ? M Vf= 250mL CiVi=CfVf Cf=CiVi Vf Cf=(2.0M)(0.63L) / .25L = 0.5M

  10. Preparing Solutions • To prepare solutions, volumetric flasks (usually 1L) are used. There is a standard procedure for preparing these solutions. • Measure out mass of solute on a scale • Partially fill the volumetric flask with water • Use a funnel to transfer the mass over to the flask. Swirl it around to dissolve the solute • Continue to add water to the line (bottom of meniscus should be at the etched line) • Transfer solution to alternate bottle (with lid) to store.

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