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shikamikonotz · Shika na Mikono

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Chapter 19: Preparation of Solutions Without a Balance

The procedure in the section on Relative Standardization (p. 66) allows us to do something seemingly impossible – prepare solutions for volumetric analysis that allow students to get perfect results without using either a balance or volumetric glassware in the preparation. All that you have to do is make two solutions that are close, and then use several cycles of relative standardization to prefect the molarity ratio.

To measure volume, we can use marks on plastic water bottles as described in the entry for volumetric glassware in the Sources of Laboratory Equipment (p. 208) section.

19.1 To make 0.05 M sulphuric acid (equivalent to 0.1 M HCl) for fifty students

  1. Put 9.9 liters of water into a bucket.
  2. Add 110 mL of battery acid. This may be accomplished easily by filling a 10 mL plastic syringe eleven times.

19.2 To make 0.033 M citric acid (equivalent to 0.1 M HCl) for fifty students

  1. Put 10 liters of water into a bucket.
  2. Add 64 g of citric acid. In the absence of a balance, one can often have 1/8 of a kilogram (125 g) measured in the market. Dissolve this in 20 L of water to produce a 0.033 M solution.

19.3 To make 0.1 M sodium hydroxide for fifty students

  1. Put 10 liters of water into a bucket.
  2. Add 40 g of caustic soda. In the absence of a balance, use a plastic syringe to find the volume of a plastic spoon. Fill the spoon with caustic soda and use it to add a total of 19 cm3 or mL caustic soda knowing the volume of each spoonful. Please read the safety note in Dangerous Chemicals (p. 37).

19.4 To make 0.1 M sodium hydrogen carbonate for fifty students

  1. Put 10 liters of water into a bucket.
  2. Add 84 g of bicarbonate of soda. In the absence of a balance, find the volume of a spoon as above and add 39 cm3 or mL of bicarbonate of soda. Alternately, if 8.33 liters of solution is sufficient, measure this volume of water and then add one whole box of bicarbonate of soda. A box is 70 g.
Updated by shikamikonotz over 4 years (view history)
Chapter 18: Preparation of Solutions Chapter 20: Relative Standardization

Contents

    Questions or Comments? Part I: Laboratory Development Chapter 1: Starting School Laboratories Chapter 2: Specific Technical Needs of a School Laboratory Chapter 3: Improving an Existing School Laboratory Chapter 4: Salvaging Old Equipment Chapter 5: Identifying Unknown Chemicals Part II: Laboratory Safety Chapter 6: Guidelines for Laboratory Safety Chapter 7: First Aid Chapter 8: Dangerous Chemicals Chapter 9: Dangerous Techniques Part III: Laboratory Management Classroom Management in the Laboratory Chapter 11: Routine Cleanup and Upkeep Chapter 12: Waste Disposal Chapter 13: Recycling Materials Part IV: Laboratory Techniques Laboratory Techniques in Chemistry Chapter 14: Use of the Beam Balance for Measuring Chemicals Chapter 15: Use of a Plastic Syringe to Measure Volume Chapter 16: Measures of Concentration Chapter 17: Calculating the Molarity of Bottled Liquids Chapter 18: Preparation of Solutions Chapter 19: Preparation of Solutions Without a Balance Chapter 20: Relative Standardization Laboratory Techniques in Biology Chapter 21: Preservation of Specimens Chapter 22: Dissection Chapter 23: Preparation of Culture Media Chapter 24: Using a Microscope Chapter 25: Low Tech Microscopy Part V: NECTA Practicals Chapter 26: Biology Practicals Chapter 27: Chemistry Practicals Chapter 28: Physics Practicals Part VI: Science Activities and Competitions Chapter 29: Hosting Science Events Chapter 30: Science Competitions Chapter 31: The Scientific Procedure Appendix A: Sources of Laboratory Equipment Appendix B: Kiswahili Laboratory Glossary Show all
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