Formula and Molecular Mass

2009 ◽  
Author(s):  
Christopher O. Oriakhi
Keyword(s):  
Phosphoric Acid ◽  
Molecular Mass ◽  
Crystalline State ◽  
Chemical Substance ◽  
Atomic Mass ◽  
Formula Unit ◽  
Actual Number ◽  
Atomic Masses ◽  
Ionic Compounds ◽  
Total Composition

Many chemists use the terms formula mass and molecular mass interchangeably when dealing with chemical compounds of known formula. But there is a slight difference between the two terms, as explained below. The formula mass of a compound is the sum of the atomic masses of all the atoms in a formula unit of the compound, whether it is ionic or molecular (covalent). The formula mass is based on the ratio of different elements in a formula, as opposed to the molecular mass, which depends on the actual number of each kind of atom (compare section 6.2, “Empirical Formula”). Formula masses are relative since they are derived from relative atomic masses. For example, the formula mass of phosphoric acid, H3PO4, is 97.98 atomic mass units (amu), which is obtained by adding the atomic masses (taken from the periodic table) of the elements in one formula unit (i.e., 3 H + 1 P + 4 O). (3×At. wt. of H)+(1×At. wt. of P)+(4×At. Wt. of O) = (3×1.00)+(1×30.97)+(4×16.00) = 97.97 Once the actual formula of a chemical substance is known, the molecular mass can be determined in a manner similar to calculating the formula mass. The molecular mass of a compound is the sum of the atomic masses of all the atoms in one molecule of the compound. The term applies only to compounds that exist as molecules, such as H2O, SO2, and glucose, C6H12O6. For example, the molecular mass of ethanol, C2H5OH, is: (2×C)+(6×H)+(1×O) (2×12.0)+(6×1.0)+(1×16.0) = 46 When ionic compounds such as NaCl, Zn(NO3)2, andNH4Cl, are in the crystalline state or in solution form, they do not contain physically distinct uncharged molecular entities. Therefore chemists often use the term formula mass to represent the total composition of such substances. Example 4.1 Calculate the formula mass (FM) of NaOH using a table of atomic masses (AM).

scholarly journals Nanomechanical Molecular Mass Sensing Using Suspended Microchannel Resonators

Sensors ◽  
2021 ◽  
Vol 21 (10) ◽  
pp. 3337
Author(s):  
Alberto Martín-Pérez ◽  
Daniel Ramos ◽  
Javier Tamayo ◽  
Montserrat Calleja
Keyword(s):  
Molecular Mass ◽  
Mass Density ◽  
Applied Pressure ◽  
Atomic Mass ◽  
Liquid Sample ◽  
Mass Sensing ◽  
Average Molecular Mass ◽  
Fluid Properties ◽  
Molecular Masses ◽  
Microchannel Resonators

In this work we study the different phenomena taking place when a hydrostatic pressure is applied in the inner fluid of a suspended microchannel resonator. Additionally to pressure-induced stiffness terms, we have theoretically predicted and experimentally demonstrated that the pressure also induces mass effects which depend on both the applied pressure and the fluid properties. We have used these phenomena to characterize the frequency response of the device as a function of the fluid compressibility and molecular masses of different fluids ranging from liquids to gases. The proposed device in this work can measure the mass density of an unknown liquid sample with a resolution of 0.7 µg/mL and perform gas mixtures characterization by measuring its average molecular mass with a resolution of 0.01 atomic mass units.

scholarly journals On the atomic masses (weights?) Of the elements

2012 ◽  
Vol 48 (1) ◽  
pp. 153-159 ◽  
Author(s):  
G. Kaptay
Keyword(s):  
Atomic Weight ◽  
Atomic Mass ◽  
Essential Information ◽  
Atomic Masses ◽  
System Of Units

Atomic masses (weights?) is an essential information for mining and metallurgy. The paper discusses four subjects around this problem. First, the classification of all the elements is suggested into 4 classes, based on their isotope features, determining the accuracy of their known atomic masses. As part of that, the class of elements is discussed with uncertain atomic weights in accordance with the 2009 IUPAC recommendations. A better (easier to use) format of atomic weights is presented for this class of elements. Third, it is found not informative to leave empty spaces instead of approximate atomic weights for elements with unstable isotopes. Fourth, the term atomic weight vs the term atomic mass is discussed shortly, in agreement with the SI system of units and in contrary to the questionable IUPAC convection.

Precise atomic masses for titanium

1979 ◽  
Vol 57 (2) ◽  
pp. 266-270 ◽  
Author(s):  
K. S. Kozier ◽  
K. S. Sharma ◽  
R. C. Barber ◽  
J. W. Barnard ◽  
R. J. Ellis ◽  
...  
Keyword(s):  
High Resolution ◽  
Mass Spectrometer ◽  
Atomic Mass ◽  
Atomic Masses ◽  
Mass Data ◽  
High Resolution Mass ◽  
University Of Manitoba ◽  
The University ◽  
High Resolution Mass Spectrometer ◽  
Resolution Mass

The 1.00 m radius high resolution mass spectrometer at the University of Manitoba ('Manitoba II') has been used to determine the atomic masses of 47Ti and 48Ti. These data are somewhat superior in precision to existing values and improve the reliability of atomic mass data in that region of the mass table.

Precise atomic masses and mass differences for mercury

1980 ◽  
Vol 58 (9) ◽  
pp. 1311-1316 ◽  
Author(s):  
K. S. Kozier ◽  
K. S. Sharma ◽  
R. C. Barber ◽  
J. W. Barnard ◽  
R. J. Ellis ◽  
...  
Keyword(s):  
High Resolution ◽  
Excellent Agreement ◽  
Mass Difference ◽  
Atomic Mass ◽  
Atomic Masses ◽  
Naturally Occurring ◽  
University Of Manitoba ◽  
The University ◽  
High Resolution Mass Spectrometer ◽  
Resolution Mass

The 1.00 m radius high resolution mass spectrometer at the University of Manitoba ("Manitoba II") has been used to determine both atomic masses and atomic mass differences for all the naturally occurring isotopes of Hg with a precision superior to existing values. The mass difference data are in excellent agreement with recently tabulated values, while the atomic masses themselves differ significantly.

AN ATOMIC MASS STUDY OF NUCLEAR SHELL STRUCTURE IN THE REGION 82 < n < 126

1954 ◽  
Vol 32 (1) ◽  
pp. 65-71 ◽  
Author(s):  
Benjamin G. Hogg ◽  
Henry E. Duckworth
Keyword(s):  
Shell Structure ◽  
Neutron Number ◽  
Atomic Mass ◽  
General Increase ◽  
Atomic Masses ◽  
Nuclear Stability ◽  
Nuclear Shell

A number of new atomic masses are reported in the region 82 < n < 126 and are used to study nuclear stability in this region. No stability effects associated with a particular neutron number are noticed but rather there is a broad general increase in stability between the 82 and 126 neutron shells.

Precise atomic masses and mass differences for W and Re

1977 ◽  
Vol 55 (6) ◽  
pp. 506-511 ◽  
Author(s):  
K. S. Sharma ◽  
K. S. Kozier ◽  
J. W. Barnard ◽  
R. C. Barber ◽  
S. S. Haque ◽  
...  
Keyword(s):  
Mass Spectrometer ◽  
Atomic Mass ◽  
Second Order ◽  
Atomic Masses ◽  
Naturally Occurring ◽  
University Of Manitoba ◽  
Double Focusing ◽  
The University

The 1 m radius, second order double focusing mass spectrometer at the University of Manitoba has been used to obtain atomic mass differences for eleven mass doublets. These data are combined with well known values for the atomic masses of 13C, l6O, 35Cl, and 37Cl to derive both atomic masses and mass differences for all of the naturally-occurring isotopes of W and Re.

New global atomic mass formulas

2017 ◽  
Vol 31 (25) ◽  
pp. 1745024
Author(s):  
William J. M. F. Collis
Keyword(s):  
Atomic Mass ◽  
Empirical Methods ◽  
Generic Point ◽  
Atomic Masses ◽  
Mass Formulas

We illustrate the improved empirical methods of estimating atomic masses using Garvey–Kelson like local relations and global equations using generic point functions.

Influence of Atomic Masses on the Coriolis Coupling Coefficients in some Symmetrical Molecules. Part III. Planar Symmetrical XY3 Molecules and Ions

1964 ◽  
Vol 19 (10) ◽  
pp. 1148-1150
Author(s):  
B. N. Cyvin ◽  
S. J. Cyvin ◽  
L. A. Kristiansen
Keyword(s):  
Molecular Model ◽  
Atomic Mass ◽  
Force Constants ◽  
Coriolis Coupling ◽  
Coupling Coefficients ◽  
Mass Ratio ◽  
Atomic Masses ◽  
Ratio Dependence ◽  
Upper Limits ◽  
Lower Limits

CORIOLIS coupling coefficients for the planar symmetrical XY3 molecular model are studied. One has found the upper limits |ζ23| → and ζ3 →· 1 with increasing atomic mass ratio mY/mX. Lower limits are also given, and appear to be functions of the force constants.Calculated ζ23 and ζ3 values for sixteen molecules (and radicals), and five ions of the considered type are reported. Curves are given for the mass-ratio dependence.

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