1 mol of carbon-12 contains 6.022x10^23 carbon-12 atoms with a mass of 12 g. Calculate the number of carbon-12 atoms in 20.0g of carbon-12.

Question

1 mol of carbon-12 contains 6.022x10^23 carbon-12 atoms with a mass of 12 g.

Calculate the number of carbon-12 atoms in 20.0g of carbon-12.

Answer 1

This is a ratio problem  

 

6.022x10^23 atoms is to 12 g as X atoms is to 20.0 g 

 

6.022X10^23 : 12  :: X : 20.0  

 

In fraction form this is (6.022x10^23 / 12) = X / 20 

 

Cross multiply to get 

 

12X = 20 * 6.022x10^23

X = (20/12) * 6.022x10^23

X = (5/3) * 6.022x10^23 = 1.003666667x10^24 = 1.004x10^24 to 3 decimal places