I have no I have no idea how to solve these problems.

Question

*I need an someone to explain to me how to solve these problems*

 

 

How many moles of tin atoms are in a pure tin cup with a mass of 42.7g ?

 

A pure gold coin contains 0.139mol of gold.
What is its mass?

 

How much money, in dollars, does one mole of pennies represent?

 

If this amount of money were evenly distributed among the entire world's population (about 6.6 billion people), how much would each person get?

 

 

 

Answer 1

Tin question: 

1. You first need to know how many grams are in 1 mole of tin, which is the mass listed on the periodic table.  118.7 grams/mol is tin's (Sn) molar mass.  

2.  Divide 42.7 grams, the weight of the pure tin cup, by 118.7 grams/mol to find out how many moles of tin that you have.

3.  You multiply the number of moles of tin that you have by Avogadro's number, 6.02 x 10²³ to get the number of atoms that you have.  Remember that Avogadro's number describes a mole of anything.  6.02 x10²³ atoms, 6.02 x1023 oranges, whatever.  It is similar to how a dozen represents 12 of anything.

 

Money question:

Given what I just said about moles, we can solve this question easily.  1 mole of pennies = 6.02 x 10²³ pennies, just like 1 dozen of donuts = 12 donuts.  So, this question is easy. We just need to convert pennies to dollars by dividing 6.02 x 10²³ by 100.

 

World distribution:

So, we have 6.02 x 10²¹ dollars.  We need to divide this up evenly amongst 6.6 billion people (6.6 x 10⁹).

 

Moles are a key quantity in that they allow us to convert certain quantities into others.  

Answer 2

For the tin cup, you need to find its molar mass. If you look on a periodic table, you'll find the atomic mass, which is the molar mass, and it is expressed in grams per mole (g/mol). So for tin, the molar mass is 118.71 g/mol. We use the molar mass to convert between moles and grams. So for a pure tin cup with a mass of 42.7 g, we would do:

 

42.7 g x    1 mol    = 0.3597 mol

    1        118.71 g  

 

So there are 0.3597 moles of tin atoms in a 42.7 gram tin cup.

 

For the gold coin, we do a similar thing. The molar mass of pure gold is 196.966569 g/mol. So to find the mass of a 0.139 mole coin, we do:

 

0.139 mol  x  196.966569 g  = 27.378 g

       1               1 mol

 

For the pennies, 1 mole equals an Avagadro's number of items (6.022 x 10²³). So it would represent that many pennies. To do the conversion to dollar just divide by 100, and we have 6.022 x 10²¹ dollars, and divided evenly among 6.6 billion people, we get 912,424,242,424, or about 900 billion per person.