Sometimes it is desirable to determine the weight percent of

Sometimes it is desirable to determine the weight percent of one element. C_1, that will produce a specified concentration in terms of t he n um be r of atoms per cubic centimeter, N_1, for an alloy composed of two types of atoms. This computation is possible using the following expression:

Solution

NA = Avogadro’s number

1 and 2 = densities of the two elements

A1 = the atomic weight of element 1 .

The concentration of component 1 in atom percent (C1 \') is just 100 c 1 \' where c 1 \' is the atom fraction of component 1. Furthermore, c 1 \' is defined as c 1 \' = N1/N where N1 and N are, respectively, the number of atoms of component 1 and total number of atoms per cubic centimeter. Thus, from the above discussion the following holds:

N1 = C1 \' N /100

N1 = C1 \' N_{A ave} / 100 A_ave

N1 = N _AC1 / [(C1 A1 /) + (A1 /2) (100 - C1)

C₁= 100 / [N1-N _AC1 / [(C1 A1 /) + (A1 /2) ] c1