9994В amu atom ) = 15.9994 amuД¬ Adding together the masses gives the molecular mass: 24.022 amuВ +В 6.0474 amuВ +В 15.9994 amu = 46.069 amuДЄlternatively, we could have used unit conversions to reach the result in one step, as described in Essential Skills 2 ( Section 3.7 'Essential Skills 2'): + + = 46.069 amu 011В amu atom ) = 24.022 amu 6 Г— atomicВ massВ ofВ hydrogen = 6 atoms ( 1. Among its many uses, ethanol is a fuel for internal combustion engines.ДЄ Determine the number of atoms of each element in the molecule.Д« Obtain the atomic masses of each element from the periodic table and multiply the atomic mass of each element by the number of atoms of that element.Д¬ Add together the masses to give the molecular mass.ДЄ The molecular formula of ethanol may be written in three different ways: CH 3CH 2OH (which illustrates the presence of an ethyl group, CH 3CH 2в€’, and an в€’OH group), C 2H 5OH, and C 2H 6O all show that ethanol has two carbon atoms, six hydrogen atoms, and one oxygen atom.Д« Taking the atomic masses from the periodic table, we obtain 2 Г— atomicВ massВ ofВ carbon = 2 atoms ( 12. The average mass of a monatomic ion is the same as the average mass of an atom of the element because the mass of electrons is so small that it is insignificant in most calculations.Д¬alculate the molecular mass of ethanol, whose condensed structural formula is CH 3CH 2OH. Because a molecule or a polyatomic ion is an assembly of atoms whose identities are given in its molecular or ionic formula, we can calculate the average atomic mass of any molecule or polyatomic ion from its composition by adding together the masses of the constituent atoms. Although the mass number is unitless, it is assigned units called atomic mass units (amu).

The mass number is an integer that is approximately equal to the numerical value of the atomic mass. To calculate the molecular mass of a covalent compound and the formula mass of an ionic compound and to calculate the number of atoms, molecules, or formula units in a sample of a substance.ДЄs you learned in Chapter 1 'Introduction to Chemistry', the mass number is the sum of the numbers of protons and neutrons present in the nucleus of an atom.

Grams to moles