The Mole Unit

Your objectives in studying this section are to be able to  

Define a kilogram mole, pound mole, and gram mole. 

Convert from moles to mass and the reverse for any chemical compound given the molecular weight. 

Calculate molecular weights from the molecular formula. 

Here is another way to look at the mole unit. To convert the number of moles to mass, we make use of the molecular weight—the mass per mole  

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The mole unit and the gram formula unit are employed in similar calculations. For this reason, many chemists use the term mole to describe quantities of both molecular and nonmolecular substances. Try answering the following problems ... 

You should recall from the review of the mole unit that the reaction coefficients (2, 1, and 2 in the preceding example) can be interpreted as molecules, or as moles, or as volumes. This is because Avogadro s law holds for all gases. The number of molecules in 1 mole of a gas is known to be... 

The definitions of the mole unit point to the necessity of specifying the species whose concentration is to be expressed. The quantity of the substance is usually expressed in moles of whole molecules, atoms or ions. However, according to the needs it can also be expressed in moles of chemical equivalents (e.g., calcium (Ca/2) = 1.00 mmol 1 ). Generally, for the conversion of the mole concentration of a substance (B) to the weight concentration the following is valid ... 

The two key points to remember about the importance of the mole unit are... 

All of the liter units cancel, as well as the mole units. The atmosphere units also cancel, leaving the unit of K (keIvins) in a denominator of the denominator, which... 

The heat capacity of a material is the amount of heat that must be introduced into a given amount of sample to raise its temperature by a given increment. The speeific heat capacity of a material can be quoted for eonstant pressure or constant volume and is given the abbreviation Cp or Q, respeetively. Various units are used for specific heat eapacity, typically being some eombination of joules or calories per mole or grams per degree Celsius. In the case of polymeric systems, the mole unit pertains to the monomer rather than the polymer as a whole. 

Barnes cautions about using the appropriate units (molecular area with mole fraction, or area per unit mass with mass fraction) when analyzing area data [244]. 

R is the gas constant per mole, while K is the temperature unit Kelvin). The dashed lines represent metastable extensions of the stable phases beyond the transition temperatures. 

Fig. 1. The dependence of the stable stationary values of the adsorption and conformational variables on the control parameter, Xe. a-total adsorption per the mole of the nucleotides, b-the probability of finding of an arbitrary NA unit in the A form, c-the probability of finding of an arbitrary NA unit in the B-form. Param-(ders values used to obtain numerical results Vmi = 3,nL = 15.4, = 3.24,6° =...

Plot the calculated first IPs as a function of the atomic number Z for the elements from H to Ne in the atomic table. The plot has a characteristic shape that should be familiar from earlier courses. These plots are frequently given in the experimental units of electron volts (eV hartrees x 27.21 = eV) or kilojoules per mole (kJ mol hartrees x 2625 = kJmol ). Write a paragraph or two in your project report explaining why the graph of IP vs. Z appears as it does. 

Chromophore (Section 13 21) The structural unit of a mole cule principally responsible for absorption of radiation of a particular frequency a term usually applied to ultraviolet visible spectroscopy... 

The moles of a species that can donate one reaction unit. 

If we know the moles of A and the number of reaction units associated with A and B, then we can calculate the moles of B. Note that a conservation of reaction units, as defined by equation 2.3, can only be applied between two species. There are five important principles involving a conservation of reaction units mass, charge, protons, electron pairs, and electrons. 

In this context the repeat units in a polymer may be divided into two classes those at the ends of the chain (subscript e) and the others which we view as being in the middle (subscript m) of the chain. The mole fraction of each category in a sample is Xg and x j, respectively. Since all segments are of one type or the other. 

The copolymer composition equation relates the r s to either the ratio [Eq. (7.15)] or the mole fraction [Eq. (7.18)] of the monomers in the feedstock and repeat units in the copolymer. To use this equation to evaluate rj and V2, the composition of a copolymer resulting from a feedstock of known composition must be measured. The composition of the feedstock itself must be known also, but we assume this poses no problems. The copolymer specimen must be obtained by proper sampling procedures, and purified of extraneous materials. Remember that monomers, initiators, and possibly solvents are involved in these reactions also, even though we have been focusing attention on the copolymer alone. The proportions of the two kinds of repeat unit in the copolymer is then determined by either chemical or physical methods. Elemental analysis has been the chemical method most widely used, although analysis for functional groups is also employed. 

Partial molar quantities have per mole units, and for Yj this is understood to mean per mole of component i. The value of this coefficient depends on the overall composition of the mixture. Thus Vj o the same for a water-alcohol mixture that is 10% water as for one that is 90% water. 

It is conventional to use molality—moles of solute per kilogram of solvent (symbol m)—as the concentration unit in electrolyte thermodynamics. Accordingly, we shall represent the concentrations of both the indifferent electrolyte and the polymer in these units in this section m3 and m2, respectively. In the same dilute (with respect to polymer) approximation that we have used elsewhere in this chapter, m2 is related to the mass volume system of units C2 by... 

Concentration. The basis unit of concentration in chemistry is the mole which is the amount of substance that contains as many entities, eg, atoms, molecules, ions, electrons, protons, etc, as there are atoms in 12 g of ie, Avogadro s number = 6.0221367 x 10. Solution concentrations are expressed on either a weight or volume basis. MolaUty is the concentration of a solution in terms of the number of moles of solute per kilogram of solvent. Molarity is the concentration of a solution in terms of the number of moles of solute per Hter of solution. 

Olefin distribution in the Albemarle stoichiometric process tends to foUow the Poisson equation, where is the mole fraction of alkyl groups in whichp ethylene units have been added, and n is the average number of ethylene units added for an equal amount of aluminum. 

These products are characterized in terms of moles of substitution (MS) rather than DS. MS is used because the reaction of an ethylene oxide or propylene oxide molecule with ceUulose leads to the formation of a new hydroxyl group with which another alkylene oxide molecule can react to form an oligomeric side chain. Therefore, theoreticaUy, there is no limit to the moles of substituent that can be added to each D-glucopyranosyl unit. MS denotes the average number of moles of alkylene oxide that has reacted per D-glucopyranosyl unit. Because starch is usuaUy derivatized to a considerably lesser degree than is ceUulose, formation of substituent poly(alkylene oxide) chains does not usuaUy occur when starch is hydroxyalkylated and DS = MS. 

Example 6 Solvent Rate for Absorption Let us consider the absorption of acetone from air at atmospheric pressure into a stream of pure water fed to the top of a packed absorber at 25 C. The inlet gas at 35 C contains 2 percent by volume of acetone and is 70 percent saturated with water vapor (4 percent H2O by volume). The mole-fraction acetone in the exit gas is to be reduced to 1/400 of the inlet value, or 50 ppmv. For 100 kmol of feed-gas mixture, how many Idlomoles of fresh water should be fed to provide a positive-driving force throughout the pacldug How many transfer units will be needed according to the classical adiabatic method What is the estimated height of pacldug required if Hqq = 0.70 m ... 

The material balance of the working unit can be formulated as follows moles per hour of TCE ( out - in) = (3/2) moles per hour soda converted. 

Table 2 illustrates the weighting method that ean be used. The required input of parameters to perform computations are the number of eomponents, the mole fraetion of ith component, the eritieal pressure of ith component in units of atm, the eritieal temperature of the ith eomponent (°K), the moleeular weight of the ith eomponent, the pressure of the mixture (atm), the temperature of the mixture ( F), and the eompressibility factor of the mixture, Z. ... 

Mole The SI unit of quantity the amount of a pure element or chemical compound that contains the same number of atoms or molecules. It is often simpler to use moles rather than volume or mass when working with gases. Moles are given by... 

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