Molecules and molecular weight

The word molecule or the general term formula unit may be applied to one unit of CO. The word atom or the term formula unit may be applied to one unit of uncombined Hg. However, there is no special name for one unit of NaCl. Formula unit is the best designation. (Some instructors and some texts refer to "molecules" of NaCl, and especially to molecular weight" of NaCl, because the calculations done on formula units do not depend on the type of bonding involved. However, strictly speaking, the terms molecule and molecular weight should be reserved for substances bonded into molecules.)... 

Physical and chemical properties Diterpenes are similar to sesquiterpenes but the larger molecules and molecular weights give them higher boiling points and lower oxidation rates. 

Discuss molecules and molecular weight in the light of the Laws of Avogadro and Gay-Lussac, vapor density, vapor tension, elevation of the boiling point, and depression of the freezing point. 

The mass m, of all molecules of species i, not their number, is measured by fractionation. The mass of all i molecules is given by the number N, of / molecules and molecular weight (m o,X of an individual molecule... 

Inspection of Table III-l shows that there is a wide range of surface tension and E values. It is more instructive, however, to compare E values calculated on an energy per mole basis. The area per mole of spherical molecules of molecular weight M and radius r is... 

One of the most important fiinctions in the application of light scattering is the ability to estimate the object dimensions. As we have discussed earlier for dilute solutions containing large molecules, equation (B 1.9.38) can be used to calculate tire radius of gyration , R, which is defined as the mean square distance from the centre of gravity [12]. The combined use of equation (B 1.9.3 8) equation (B 1.9.39) and equation (B 1.9.40) (tlie Zimm plot) will yield infonnation on R, A2 and molecular weight. 

The analyses which follow are arranged in the order in which they would be applied to a newly discovered substance, the estimation of the elements present and molecular weight deter-minations(f.e., determination of empirical and molecular formulae respectively) coming first, then the estimation of particular groups in the molecule, and finally the estimation of special classes of organic compounds. It should be noted, however, that this systematic order differs considerably from the order of experimental difficulty of the individual analyses. Consequently many of the later macro-analyses, such as the estimation of hydroxyl groups, acetyl groups, urea, etc. may well be undertaken by elementary students, while the earlier analyses, such as estimation of elements present in the molecule, should be reserved for more senior students. 

Mitochondria are surrounded by a simple outer membrane and a more complex inner membrane (Figure 21.1). The space between the inner and outer membranes is referred to as the intermembrane space. Several enzymes that utilize ATP (such as creatine kinase and adenylate kinase) are found in the intermembrane space. The smooth outer membrane is about 30 to 40% lipid and 60 to 70% protein, and has a relatively high concentration of phos-phatidylinositol. The outer membrane contains significant amounts of porin —a transmembrane protein, rich in /3-sheets, that forms large channels across the membrane, permitting free diffusion of molecules with molecular weights of about 10,000 or less. Apparently, the outer membrane functions mainly to... 

Consider the substance hydrogen chloride. This compound has the molecular formula HQ. A chemist working with hydrogen chloride, HQ, must often know the weight of a mole of molecules (the molecular weight). This weight is readily calculated from the atomic weights of the two kinds of atoms, H and Cl ... 

The mitochondrion has an outer and an inner membrane (Figure 1). The outer membrane contains pores formed from a protein, porin, which allow exchange of molecules with molecular weights up to about 2,000 between the cytosol and the intermembrane space. The inner membrane is extensively invaginated to increase its surface area. It has a different lipid composition from the outer membrane and is rich in the acidic phospholipid cardiolipin (diphosphatidyl-glycerol) which is only found in animal cells in mitochondria. Cardiolipin confers good electrical insulating properties on the inner membrane which is impermeable... 

Electrospray ionization, in contrast to the majority of other ionization methods employed in mass spectrometry, produces predominantly multiply charged ions of the intact solute molecule. This effectively extends the mass range of the mass spectrometer and allows the study of molecules with molecular weights well outside its normal range. 

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