What is the composition in weight percent of an alloy that contains 98 g tin and 65 g lead? what is the composition in atom percent?

See explanation below for answer

Explanation:

We'll do this question in two parts:

a) Weight percent of the alloy:

This is pretty easy, all we have to do is to sum the mass of each element in the alloy and then, divide each mass between the total to get the percentage in weight. In other words:

%W = m/mtotal * 100

The total mass:

mtotal = 98 + 65 = 163 g

%Sn = 98/163 * 100 = 60.12%

%Pb = 65/163 * 100 = 39.88%

b) atom percent of the alloy:

In this case, we do something similar that in part a) with the difference that instead of using mass, we will use moles of each element. The molar mass of Tin and Lead reported are 118.71 g/mol and 207.2 g/mol. The expression to use will be:

C = n/ntotal * 100

so for each element, the moles are:

moles Sn = 98/118.71 = 0.8255 moles

moles Pb = 65/207.2 = 0.3137 moles

the total moles:

ntotal = 0.8255 + 0.3137 = 1.1392 moles

So the composition in atoms for each element is:

C Sn = 0.8255/1.1392 * 100 = 72.46%

C Pb = 0.3137/1.1392 * 100 = 27.54%