change from grams to mole units

Question

10.65g of BaBr₂

Answer 1

Get the molecular weight of BaBr₂

Divide 10.65 grams by molecular weight ... you get number of moles.

Good luck!!

Answer 2

Hi Oscar,

 

The first thing you need to do is find the formula weight for BaBr_2.  You can find the atomic weight (or mass) of each element in the periodic table.  If you look up Ba (barium) you will see that it weighs 137.3 grams/mole, and Br (bromine) weighs 79.9 grams/mole.  (I've seen variations in periodic tables, so if the weights in your table are a little off, don't worry about it.)  Since there are 2 atoms of Br, multiply 79.9 x 2 = 159.8 .  Add that to the weight of Ba:  137.3 + 159.8 = 297.1 g/mol .  So 1 mole of BaBr2 is equal to 297.1 grams, which can be written as 297.1g/mol or mol/297.1g.  Use whichever conversion works in the equation so that the proper units cancel out. 

 

Now we can convert 10.65 grams to moles by using the g/mol conversion of BaBr₂ :

 

10.65 g BaBr₂ x  (1 mole BaBr2 / 297.1 g BaBr2)  = 0.036 mol BaBr2

 

The grams cancel out so we end up with moles of substance.   

 

Use this method to answer the other question you posted.  

 

Hope that helps.

Answer 3

Molecular wt. of BaBr₂ = 56 + (35x2) = 126

 

126g = 1 mole

10.65 g = 10.65/126 =0.0845 moles

:)