Calculating the Composition of an Alloy

What is the composition, in weight percent, of an alloy that consists of 6 at% Pb and 94 at% Sn?

a) 6% Pb, 94% Sn
b) 60% Pb, 40% Sn
c) 94% Pb, 6% Sn
d) 40% Pb, 60% Sn

Final answer:

The weight percent composition of an alloy consisting of 6 at% Pb and 94 at% Sn is approximately 10.02% Pb and 89.98% Sn, using atomic mass and percent composition calculations. Hence, all options are incorrect.

Explanation:

An alloy consisting of 6 atomic percent (at%) Pb and 94 at% Sn, we must take into account the atomic masses of lead (Pb) and tin (Sn). From the provided information, we understand that one mole of Pb (207 g) and one mole of Sn (118.7 g) each contain 6.022 × 10²³ atoms.

To represent 6 at% Pb and 94 at% Sn, we will consider a sample of 100 atoms. This gives us 6 atoms of Pb and 94 atoms of Sn. Thus, the total mass of Pb in the alloy is 6 atoms × 207 g/mol = 1242 g (since 1 mole of atoms is 207 g of Pb), and the total mass of Sn is 94 atoms × 118.7 g/mol = 11158.8 g.

Adding these together gives the total mass of the alloy: 1242 g + 11158.8 g = 12400.8 g. To find the weight percent of Pb: (1242 g/12400.8 g) × 100 = 10.02% Pb and for Sn: (11158.8 g/12400.8 g) × 100 = 89.98% Sn. Therefore, the correct answer is that the composition by weight percent of the alloy is 10.02% Pb and 89.98% Sn.