Book contents
- Frontmatter
- Contents
- Introduction
- How important is maths in data-handling?
- Abbreviations and the Système International
- Acknowledgements
- 1 Numbers and indices
- 2 A sense of proportion
- 3 Graphs
- 4 Algebra
- 5 Logarithms: exponential and logarithmic functions
- 6 Simple statistics
- 7 Preparing solutions and media
- 8 Enzymes
- 9 Spectrophotometry
- 10 Energy metabolism
- 11 Radioactivity
- 12 Growth in batch cultures
- 13 Growth in continuous culture
- 14 Microbial genetics
- 15 Problems
- 16 Advice and hints
- 17 Answers to problems
- Conclusion
- Further reading
- Index
7 - Preparing solutions and media
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Introduction
- How important is maths in data-handling?
- Abbreviations and the Système International
- Acknowledgements
- 1 Numbers and indices
- 2 A sense of proportion
- 3 Graphs
- 4 Algebra
- 5 Logarithms: exponential and logarithmic functions
- 6 Simple statistics
- 7 Preparing solutions and media
- 8 Enzymes
- 9 Spectrophotometry
- 10 Energy metabolism
- 11 Radioactivity
- 12 Growth in batch cultures
- 13 Growth in continuous culture
- 14 Microbial genetics
- 15 Problems
- 16 Advice and hints
- 17 Answers to problems
- Conclusion
- Further reading
- Index
Summary
Round about the cauldron go;
In the poison'd entrails throw.
William ShakespeareAmounts and concentrations
Many students have great difficulty in distinguishing clearly between amounts of a substance, and the concentration of a substance in a solution, or the proportion of a substance in a mixture.
An amount is a definite quantity of a solid, liquid or gas. Examples are: 10 mg anhydrous potassium nitrate; 1 g of 10m sulphuric acid; 25 ml of 2m sulphuric acid; 10 L hydrogen (at STP); 3 ml of 0.9% (w / v) sodium chloride in water; 2 × 107 staphylococci; 5 mmoles ammonium sulphate.
The relative molecular mass (abbreviated RMM or mol. wt) of a substance, expressed in grams, is one mole of that substance. A mole (abbreviated mol) is a definite quantity of a substance, even if the RMM of that substance is not known, because the number of molecules in one mole of any pure substance is always 6.02 × 1023 (Avogadro's number). This is not the same as the number of atoms in a molecule; for example oxygen or hydrogen gases each have 2 atoms per molecule, methane has 5 atoms per molecule while glucose has 24 atoms in its molecule.
A concentration is an expression of proportion, whether this is for example the strength of a solution or the percentage of an organism that is nitrogen. Knowing a concentration is very important, but the concentration, of itself, does not tell the amount of material.
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- Data-Handling in Biomedical Science , pp. 64 - 72Publisher: Cambridge University PressPrint publication year: 2010