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Lab 3

Lab 3. Solutions Mathematic exercises. Solution preparation is one of the most essential skills of a biotechnology lab employee. Solutions are mixtures in which one or more substances are dissolved in another substance. Solid solutes are measured on balances or scales.

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Lab 3

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  1. Lab 3 Solutions Mathematic exercises

  2. Solution preparation is one of the most essential skills of a biotechnology lab employee. Solutions are mixtures in which one or more substances are dissolved in another substance. Solid solutes are measured on balances or scales. Concentration is measured in several ways: Mass/volume Volume/volume % mass/volume Molarity Normality Making Solutions

  3. Making Mass/Volume Solutions Ex. Prepare 50 ml a solution of 15 g/L: A) 15 g/1000 mL x 50 mL = 0.750 g OR:0.75 g B)15 g --------------------- 1 000 m L X ----------------------- 50 mL X = 50 x 15 1 000 Concentration in Volume/Volume Units Ex. mL/L, uL/ml

  4. Percentage solutions Percentage – a proportion of something out of 100 parts, expressed as a whole number 1) Weight/ weight: 15% NaCl (m/m) = 15 g of NaCl + 85 g of water. 85 g of water is equal to 85 mL. 2) Weight/volume: 15% NaCl in water (= 15 g of NaCl in a total volume of 100 mL of water) 3) Volume/Volume: 15 % glycerol in water: 15 g glycerol in a total volume of 100 mL of water, or: 150 mL y 100o mL…

  5. Molar Concentrations One mole is equivalent to the molecular weight of a given substance, reported in grams 1 Molar is 1 mole per Liter 1 mole= Molecular weight expressed in g Molarity Concentration Equation volume molarity molecular the number of grams to be wanted (L) X desired X weight of the = dissolved in solvent, up to (mol/L) solute (g/mol) the total volume of solution desired Ex. Prepare 10 ml of a 0.1 M solution of NaOH (MW= 40): 0.010 x 0.1 x 40 = 0.04 Wigh 0.04 g of NaOH, dissolve in less than 10 ml, and make up volume to 10 mL

  6. Stock Solutions:Concentrated solutions prepared to be diluted to the working solution when needed Ex. TAE Buffer 50 X When used, the stock solution should be diluted 50 times: Prepare 100 mL of TAE 1 X: We use this formula: VC=VC What volume do I have to take from a solution which has a given concentration (50 X) to prepare a specific volume of a solution at the desired concentration?

  7. X (ml) . 50 (x) = 100 mL . 1 (What volume of the 50 x solution to prepare 100 ml of a 1 x solution). • X= 100 . 1 X= 50 50 • Take 50 mL and make up volume to 100 ml with water or the appropriate dissolvent

  8. Dilutes of Concentrated Solutions Diluting a 100 mg/mL Stock Solution to 1 mg/mL. VC=VC X (mg). 100 (mg/ml) = 1 000 (ml) . 1 (mg/ml) X= 10 ml

  9. PROCEDURES • Pg 35: Procedure 2 • Pg. 36-37: Procedure 4

  10. HOMEWORK Practice problems, Seidman & Moore, 2000 • Weight/Vol Pg. 451, Questions No. 3 • Molarity Pg. 455, Questions No. 1, 3, 5 • Percents: Pg. 458, Questions No. 1, 2, 6 • Stock Solutions: Pg. 479, Questions No. 1, 2, 5

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