Simple Solutions and Dilutions

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Simple Solutions and Dilutions

• Review of solutions

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A Solution

• Solution a solution is created by dissolving a
  solute into a solvent
• Solute substance being dissolved
• Solvent substance doing the dissolving
  (typically a liquid)

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Concentration

• Concentration is measured by the amount of a
  solute dissolved by the solvent
• Percent concentration parts per hundred
• Solute (in dry grams) / volume (100 ml) of
  solvent
• Molarity is a common chemistry unit of
  concentration
• of moles of solute / 1 dm3 of total solution

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Types of Dilutions

• Simple dilutions unit volume of a liquid
  material combined with a unit volume of solvent
  liquid
• Molarity by dilution a specific conc is diluted
  to a new conc with a set volume
• Percent Solutions reagents are mixed as percent
  concentrations
• Molar Solutions moles / liter of solution
• Serial Dilutions a series of dilutions this
  amplifies the dilution factor with each step

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Simple Dilutions

• Solute and solvent are mixed as parts
• Written as a ratio 15 and verbalized as 1 part
  to 5 parts
• Parts are equal volumes
• Frozen orange juice is a simple dilution

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Molarity by Dilution

• Requires a specific conc that must be diluted to
  a set volume and conc
• Molarity is a unit of concentration
• M1V1 M2V2 (Molarityvolume)
• V1C1 V2C2 (VolumeConc)
• Most common dilution used in chemistry

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Percent Solutions

• Reagents are mixed as percent conc
• grams (dry chemical) / 100 ml of solvent
• To make a 3 NaCl solution you would use 3.0g
  of NaCl and 100 ml of H2O
• ml liquid in 100ml total final volume
• To make a 70 ethanol from 100 ethanol use 70
  ml of 100 ethanol and add 30 ml of water

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Molar Solutions

• Moles / liter of solution
• If Molarity is known - the volume needed and the
  formula mass of the solute must be used to
  calculate the number of moles
• Volume needed (moles/L of soln) FM

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Serial Dilutions

• Used most commonly in microbiology and
  biotechnology with cells or organisms
• Serial dilutions are usually made in increments
  of 1000, 100, or 10
• Concentration of the original soln and the
  desired conc will determine how great and how
  many dilutions will occur
• Technique involves removing a small volume of
  original soln to another container and bringing
  it up to the original volume using buffer or water

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Serial Dilutions cont

• If you have 1 ml of your original soln, you
  remove 10 µl and place it in a tube containing
  990 µl of water or media you now have 1100
  dilution
• If the original soln contained 5 x 10 8
  cells/ml, now the new tube contains 5 x 10 6
  cells/ml because we divided the conc by 100

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Serial Dilutions cont
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Micropipetting

• Make sure the correct volume is always set before
  you start
• Use in an aseptic setting if working with a
  culture
• Be careful to not contaminate your tip or sample
  always use a clean tip if necessary