15. concentrartion of solutions

• 15 two glasses of honey water with differens, unts (in spoonful) of the honey to oney water will have different concem queous solutions of a chemical in more concentrated solution of the.
• 1 dm


  10 cm
• 1 dm³


  1000 cm³
• Concentration of solutions


  The amount of solute in a unit volume of the solution, usually expressed in g dm³ and mol dm³
• Calculating concentration of solutions in g dm³

  Mass of solute / Volume of solution (dm³)
• Molarity (molar concentration)


  The number of moles of solute per dm³ of solution
• Calculating concentration of solutions in mol dm³

  Number of moles of solute / Volume of solution (dm³)
• Conversion between mol dm³ and g dm³

  Concentration in g dm³ = Molarity (mol dm³) x Molar mass of solute (g mol⁻¹)
• Converting concentration unit from g dm³ to mol dm³

  Molarity (mol dm³) = Concentration (g dm³) / Molar mass of solute (g mol⁻¹)
• Concentration of aqueous bench solutions are usually stated in molarity (mol dm³), rather than in g dm³
• Density of solution


  Percentage by mass of solute in solution
• Calculating number of moles of solute from molarity and volume


  Number of moles = Molarity x Volume (dm³)
• Calculating mass of solute from volume and molarity


  Mass of solute = Number of moles x Molar mass
• Calculating volume of solution from number of moles and molarity

  Volume = Number of moles / Molarity
• Calculating molar concentration of constituent ions


  Moles of ion / Volume of solution
• Concentrated solutions are often diluted to a solution of a particular concentration
• Example 15.9


  • Calculating the molar concentration of the constituent ions in a resultant solution
• Calculating the molar concentration of the constituent ions in a resultant solution


  1. Number of moles of NaCl

  2. Number of moles of Na+ from NaCl

  3. Number of moles of Na2SO4

  4. Number of moles of Na+ from Na2SO4

  5. Number of moles of Na+ in the resultant solution

  6. Volume of the resultant solution

  7. Molar concentration of Na+(aq) in the resultant solution
• Dilution of a solution
• Concentration of the solution decreases after dilution
• Example 15.10


  • Calculating the molarity of a diluted solution
• Example 15.11


  • Calculating the volume of water required for dilution
• Concentration of solutions
• Diluted bleach solution
• Dilution


  The process of reducing the concentration of a solution by adding more solvent
• Number of moles of solute remains unchanged during dilution
• Concentration of the solution decreases as the same number of moles of solute is dissolved in a larger volume of solvent
• To dilute 100 cm3 of 2.0 M NaOH solution to 0.2 M, 1000 cm3 of water is needed
• To dilute 100 cm3 of 2.0 M NaOH solution to 1.2 M, 90 cm3 of water is needed
• Concentration can be expressed in g/dm3 and mol/dm3
• Molarity (or molar concentration)


  Number of moles of solute (mol) / Volume of solution (dm3)
• Concentration of a solution (g/dm3)

  Molarity of solution (mol/dm3) x Molar mass of solute (g/mol)
• Calculations related to the concentration of solutions

  Number of moles of solute (mol) = Molarity of solution (mol/dm3) x Volume of solution (dm3)

  Volume of solution (dm3) = Number of moles of solute (mol) / Molarity of solution (mol/dm3)

  Mass of solute (g) = Molarity of solution (mol/dm3) x Volume of solution (dm3) x Molar mass of solute (g/mol)
• Concentration of solutions


  The amount of solute present in a given volume of the solution, usually expressed in g dm³ and mol dm³.
• Solute


  The substance that is being dissolved in a solution. It can be a solid, liquid, or gas.
• Solution


  A homogeneous mixture of two or more substances. In a solution, the solute is dispersed uniformly throughout the solvent (the substance doing the dissolving).
• Volume


  The amount of space occupied by a substance. In this case, we're referring to the volume of the solution.
• g dm³


  Grams per decimeter cubed. A unit of concentration that measures the mass of solute per unit volume of the solution.
• mol dm³


  Moles per decimeter cubed. A unit of concentration that measures the number of moles of solute per unit volume of the solution.
• Solution


  A homogeneous mixture of two or more substances, where a solute is dispersed uniformly throughout a solvent.