MOLAR MASS

Molar mass: The molar mass is the mass, in grams, of one mole of a substance. The molar mass is numerically the same as the formula mass (found in the periodic table) but with units of grams mol-1.


We use grams per mol = g/mol


To calculate the molar masses:

Here are some other examples:


Calculate the molar masses of:


Mg(OH)2


24.3 + 2(16) + 2(1) = 58.3 g/mol


(NH4)2SO4


2(14.0)+8(1.0)+32.1+4(16.0)= 132 g/mol


Now let's try some Molar Conversions...


Mr. Doktor gave us a handy chart we can refer to when we are doing our conversions! Look below:

Now let us try shall we...
oh yeah before I forget, remember to use Avogardo's top secret number when you are trying to find the number of atoms, formula units, or moles! Whats his secret number? 
Highlight the bottom space under this to find out....


6.02 x 10²³
Now dont tell anyone and use this number to your advantage.... haha


A sample of Carbon contains 2.47x10²5 atoms. How many moles of carbon is this?


2.47x10²5 atoms x 1 mol/ 6.02 x 10²³ atoms = 41.02990033 moles
*Round to sig figs
= 41.0 moles


How many atoms are there in 1.5 mol of Iron?
(If your stuck, start off with what you're given!)


1.5 mol x 6.02 x10²³atoms/1 mol= 9.03 x10²³ atoms 
... but you only get 1/2 marks because you forgot sig figs! so remember your sig figs and you get....


= 9.0 x 10²³ atoms


12.5 moles of 0² represent how many molecules?


12.5 mol x 6.02x10²³molecules/ 1mol = 7.52 x ²4 molecules


Find the mass of 0.159 mol of SiO2


0.159mol x 60.1 g/1mol = 9.5559g
=9.56g


Get the drift? If yes than good for you now go away! If no, then lets do one more with a more detailed explanation. Lets try the a similar example to the last example I did.


Find the mass of 3.66 mol of N²


Write what you're given:


3.66 mol


Now you want to get rid of moles and you want to find the mass. Mass is measured in grams (g) and since N (nitrogen) is diatomic (which you can also depict from the subscript 2 however that 2 should not be on the top right it should be on the bottom...) then you can write your equation like this:


3.66 mol x 28 g / 1 mol


28 grams came from Nitrogens Atomic mass in the periodic table which is 14 but times 2! 14x 2 = 28!


3.66 mol x 28g/ 1 mol
Cancel your units.... 
(3.66) x (28)
and you get ....
102 grams!




Now you know how to convert mole conversions! More coming later!


-Post by Ren Flores