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Making Solutions of Differing % Mass/Volume Concentrations Lab Manual 3F.

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Presentation on theme: "Making Solutions of Differing % Mass/Volume Concentrations Lab Manual 3F."— Presentation transcript:

1 Making Solutions of Differing % Mass/Volume Concentrations Lab Manual 3F

2 timeline Monday—Lecture Tuesday—Perform Lab Part I, II, III Thursday—Perform Lab Part IV

3 Write-up  Procedures (all will do the additional concentrations)—part IV #4  Data (include additional concentrations) (include additional concentrations).3125% and.15625%  Data Analysis/Conclusion (answer all questions in from the text)  Thinking Like a Biotechnician--#1,2,4 (Skip 3)— do 4 on notebook paper

4 Prep. for 3f  Check for sodium hydroxide pellets, cupric sulfate 5 hydrate, gelatin, glass tubes  Set-up spectrophotometer

5 Background Application Example  Fertilizer—”12-5-7” 12% nirogen, 5% phosporus 7% potassium in the 5 lb bag.12 x 5lb=.6lb nitrogen.05 x 5lb=.25lb phosphorus.07 x 5lb-.35lb potassium

6 Background Biuret reagent  Copper sulfate and sodium hydroxide make up a protein indicator called Biuret reagent  2 to 1 ratio of 10% sodium hydroxide and 5% copper sulfate  When the copper reacts with certain amino acids in proteins, the solution goes from blue green or violet.  The darker violet the solution, the more protein is present  Copper also used as an indicator in Bradford reagent & BCA reagent as a protein indicator & in Benedict’s solution for glucose

7 Background  Copper sulfate is only good for about 1 week before precipitating out  Gelatin is made from fairly large protein molecules that do not easily go into solution, this is why gelatin must be heated to go into solution.  The protein testing should be conducted at room temperature, so you need to plan ahead  Gelatin solutions are fairly concentrated, to get obvious color difference

8 Formulas  Volume desired (ml) x concentration desired (% g/ml converted to decimal value of g/ml)= ____g of solute

9 Safety Precautions  Sodium hydroxide is dangerous (wear gloves and googles)—strong base  Use hot plates not a flame

10 Lab 3F tips  Do calculations in advance—show how units cancel  When making a solution, the solute is measured out first, and the solvent is mixed into the solute  The mass takes up space, solutions are always prepared by raising the solvent to the final volume

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