Units and 1 Conversion Factors

The base units of measurement under the Systeme International d Unites, or SI units, are given in Table 2.1 [3]. 

Some Sl-derived units with special names are included in Table 2.2. The standard atmosphere may be used temporarily with SI units it is dehned to be equal to 1.01325 X 10 Pa. The thermochemical calorie is no longer recommended as a unit of energy, but it is defined in terms of an SI unit, joules, symbol J, as 4.184 J [4]. The unit of volume, liter, symbol L, is now defined as Idm.  

The authoritative values for physical constants and conversion factors used in thermodynamic calculations are assembled in Table 2.3. Furthermore, information about the proper use of physical quantities, units, and symbols can be found in several additional sources [5]. 

For example, for uranium, this means that, after elemental uranium and its monoatomic ions ), the uranium compounds and complexes with oxygen 

The references cited in the review are ordered chronologically and alphabetically by the first two authors within each year, as described by CODATA [1987GAR/PAR]. A reference code is made up of the four digits of the year of appearance, followed by the first three letters of the surnames of the first two authors, separated by a slash. 

If there are multiple reference codes, a 2 will be added to the second one, a 3 to the third one, and so forth. Reference codes are always enclosed in sqnare brackets. 

Thermodynamic data are given according to the Systeme International d unites (SI units). The unit of energy is the joule. Some basic conversion factors, also for non-thermodynamic units, are given in Table II-4. 

To convert from (non-SI unit symbol) to (SI unit symbol) multiply by 

Every held has its own special units of measure and nuclear chemistry is no different. The unit of length is the femtometer (10-15 m), which is called a fermi. The unit of mass is the atomic mass unit (amu or u), which has a numerical value of 1.66 x 10 24 g or expressed in units of MeV/c2, it is 931.5 MeV/c2. The unit of energy is MeV (106eV), which is 1.602 x 10 13 J, the energy gained when a proton is 

Engineering is about real physical things, which can be measured and described in terms of the units of measure. Most engineering calculations involve these units of measure. It would be simple if there were only one set of such units that the whole world agreed on and used, but that is not the case today. In the United States, most measurements use the English system of units, based on the foot, pound, and degree Fahrenheit, but most of the world uses the metric 

In fluid mechanics, most often we deal with dimensioned quantities, such as 12ft/s( = 3.66m/s), rather than with pure numbers, such as 12 or 3.66. To become competent at sblving fluid mechanics problems, you must become virtually infallible in the handling of such units and their conversion factors. For most engineers the major sources of difficulties with units and conversion factors are carelessness and the simultaneous appearance of force and mass in the same equation. j 

A useful system for avoiding carelessness and consistently converting the dimensions of engineering quantities from one set of units to another has two rules j 

Always (repeat, alv fays) include the dimensions with any engineering quantity you write down. 

Convert the dimensic ns you have written down to the dimensions you want in your answer by multiplying or dividing by 1. 

The International Union for Pure and Applied Chemistry (lUPAC) recommends the adoption in scientific publications of the SI system notation. Tables A 1.1 and A1.2 present the base units and some derived units. 

In geochemical literature, one often encounters non-SI units (e.g., bar, atmosphere, calorie, angstrom, electron-volt, etc.), which can be converted to SI units by the use of simple multiplicative factors, as shown in table A1.3. 

Of particular practical interest are the general energy conversion factors (Lewis and Randall, 1970) presented in table A1.4. 

As we have already seen, the mole is the mass unit in the SI system. The molar concentrations of components in geochemical systems assume different significances as a function of the adopted reference unit  

Mole = amount of substance, expressed in weight (g), containing Avogadro s number of molecules of the substance of interest Molality = moles of solute per kg of solvent Molarity = moles of solute per 10 m of solution Formality = moles of solute per kg of solution 

In 1954, the 10th CGPM added the degree Kelvin as the unit of temperature and the candela as the unit of luminous intensity. At the time of the 11th CGPM in 1960, this new system with six base units was formalized with the tide International System of Units. Its abbreviation in all languages is SI, from the French l e Sjstume International d Unitus. 

In order to increase the precision of realization of the base unit meter, the definition based on the wavelength of a krypton-86 radiation was replaced in 1983 by one based on the speed of light. Also added were the prefixes zetta (Z) for 10, zepto (z) for 10 , yotta (Y) for 10 , and yocto (y) for 10 . 

In 1995 the 20th CGPM approved eliminating the class of supplementary units as a separate class in SI. Thus the new SI consists of only two classes of units base units and derived units, with the radian and steradian subsumed into the class of derived units of the SI. 

SI is a decimal system. Fractions have been eliminated, and multiples and submultiples are formed by a system of prefixes ranging from yotta, for 10 , to yocto, for 10 . Calculations, therefore, are greatiy simplified. 

Each physical quantity is expressed in one and only one unit, eg, the meter for length, the kilogram for mass, and the second for time. Derived units are defined by simple equations relating two or more base units. Some are given special names, such as newton for force and joule for work and energy. 

Since a large part of the NEA-TDB project deals with the thermodynamics of aqueous solutions, the units describing the amount of dissolved substance are used very frequently. For convenience, this review uses M as an abbreviation of mol-dm for molarity, c, and, in Appendices B and C, m as an abbreviation of mol-kg for molality, m. It is often necessary to convert concentration data from molarity to molality and vice versa. This conversion is used for the correction and extrapolation of equilibrium data to zero ionic strength by the specific ion interaction theory, which works in molality units (c/ Appendix B). This conversion is made in the following way. Molality is defined as moles of substance B dissolved in 1 kilogram of pure water. Molarity is defined as Cg moles of substance B dissolved in (/ - c M) kilogram of pure water, where p is the density of the solution in kg-dm and the molar weight of the solute in kg-mof.  

When the ionic strength is kept high and constant by an inert electrolyte, I, the ratio OTb /cb can be approximated by  

Baes and Mesmer [76BAE/MES], (p.439) give a table with conversion factors (from molarity to molality) for nine electrolytes and various ionic strengths. Conversion factors at 298.15 K for twenty four electrolytes, calculated using the density equations reported by Sohnel and Novotny [85SOH/NOV], are reported in Table 11-5. 

It should be noted that equilibrium constants need also to be converted if the concentration scale is changed from molarity to molality or vice versa. For a general equilibrium reaction, 0 = X b b the equilibrium constants can be expressed either in molarity or molality units, or, respectively  

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Basic Standards for Chemical Technology. There are many numerical values that are standards ia chemical technology. A brief review of a few basic and general ones is given hereia. Numerical data and definitions quoted are taken from References 16—19 (see Units and conversion factors) and are expressed ia the International System of Units (SI). A comprehensive guide for the appHcation of SI has been pubUshed by ASTM (20). 

Units. The SI system of units and conversion factors (qv) has been formally adopted worldwide, with the exception of Bmnei, Burma, Yemen, and the United States. The participation of the United States in the metrication movement is evident by the passage of the Metric Acts of 1866 and 1975 and the subsequent estabUshment of the American National Metric Council (private) and the U.S. Metric Board (pubHc) to plan, coordinate, monitor, and encourage the conversion process. 

Pressure is defined as force per unit of area. The International System of Units (SI) pressure unit is the pascal (Pa), defined as 1.0 N /m. Conversion factors from non-SI units to pascal are given in Table 1 (see also Units and conversion factors front matter). An asterisk after the sixth decimal place indicates that the conversion factor is exact and all subsequent digits are 2ero. Relationships that are not followed by an asterisk are either the results of physical measurements or are only approximate. The factors are written as numbers greater than 1 and less than 10, with 6 or fewer decimal places (1). 

Designers, manufacturers, and operators of boilers continue to use many of these terms, without undue deference to unit standardization, to define, measure, and report on plant steam-raising capacities power output) and operating parameters. (In continuance of this common practice therefore, many of these various terms are freely used in discussions throughout this book.) However, to familiarize the reader and minimize confusion, some energy terms and notes are provided here. A more complete list of units and conversion factors is provided in the appendix. 

Length -definition of [MATERIALS STANDARDS AND SPECIFICATIONS] (Vol 16) -measurement of [UNITS AND CONVERSION FACTORS] (Vol 24)... 

Since density always has two units, and conversion factors have two units, guess what Density is a conversion factor between mass and volume. Don t memorize when you need to multiply by density or divide by density to achieve a required conversion. Let the units tell you what to do. 

Appendix 8 Chemical and physical constants, units and conversion factors... 

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