General Features of SI Units

As Table 1.1 shows, the SI system is based on a set of seven fundamental units, or base units, each of which is identified with a physical quantity. All other units, called derived units, are combinations of these seven base units. For example, the derived unit for speed, meters per second (m/s), is the base unit for length (m) divided by the base unit for time (s). (Derived units that occur as a ratio of 

Common Decimal Prefixes Used with SI Units 

Prefix Prefix Symbol Word Conventional Notation Exponential Notation 

Let s discuss some of the SI units for quantities that we use early in the text length, volume, mass, density, temperature, and time. (Units for other quantities are presented in later chapters, as they are used.) Table 1.3 shows some useful SI quantities for length, volume, and mass, along with their equivalents in the English system. 

Quantity SI SI Equivdents English Equivalents English to SI Equivalent 

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General Features of SI Units 14 Some Important SI Units in Chemistry 14 Extensive and Intensive Properties 20... 

An excellent source of information about the SI can be found at the website of the US National Institute for Standards and Technology (NIST) http //physics. nisLgov/cuu/Units/index.html Here we shall be mainly concerned with those quantities that directly affect quantitative measurements of amounts of chemical substances by mass spectrometry. However, it is appropriate to briefly describe some general features of the SI. 

XRD pattern of the MCM-41 sample synthesized in the present work was presented in Figure 1. The XRD pattern was comprised of one very intense line, three weak lines, which could be indexed to (100), (110), (200), and (210) diffraction lines characteristic of a hexagonal structure of MCM-41, respectively. This feature was generally attributed to the formation of Si-O-Si bonds by condensation of Si-OH groups present in the as-synthesized material. The hexagonal unit cell (ao) could be calculated by Eq. (1)... 

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