Precent by Mass

Question

An alloy is 12.2% Copper by mass in Tin. Copper makes up what percent of the atoms in this sample?

Answer 1

Hello, Libby,

Alloy:

Tin (Sn) = 87.8%

Copper (Cu) = 12.2%

Assume 100 grams (for convenience)

Mass (g) Molar Mass Moles (the numbers of atoms)

(g/mole)

Sn 87.8 g 118.7 0.740

Cu 12.2 g 63.5 0.192

Total moles = 0.932 [Note: 0.932 x 6.023x10²³ would be equal to the total atoms of Sn and Cu]

Percent Cu = 0.192/0.932 = 20.6%

Bob