Question

How many moles of tin atoms are in a pure tin cup with a mass of 37.6 g ?

Answer 1

Tin is an element called Stannum and has the symbol Sn. Molar mass is the mass of 1 mol of a compound, 1 mol of any substance is made of 6.022 x 10²³ units, these units could be atoms making up an element or molecules making up a compound. 
While the number of atoms making up 1 mol is the same for any element, the weight of 1 mol of substance varies from one another.
In tin(Sn) molar mass - 118.71 g/mol
In 118.71 g - there's 1 mol of tin
therefore in 37.6 g of tin - 1 x 37.6 / 118.71 = 0.31 mol 
In 37.6 g of tin, there's 0.31 mol