How can I calculate Molarity?

4 ANSWERS

1. Tom Reeds
   

   Molarity is a way of expressing the concentration of any solution. It is defined as number of moles which are dissolved in one litre of solution and it is also known as moles per litre. Rather than writing moles per litre, it is abbreviated by M, and it means moles per litre not just moles. There is a difference between moles and molarity. Molarity measures the concentration of the material.
   Molarity is calculated by the following formula,
   It is
   Molarity = Grams/ (Molecular Weight x Volume)
   While the formula for moles is Moles/liter = Grams/{ (grams/mole) x liters}
    

   Report (0) (0)  |   1 year, 1 month(s) ago  

2. Guest3934
   

   21.25 grams/169.9 grams/mol/0.5 liters = 0.2501 M
   
   parts per million = mg /liter = ug/mL
   
   so if there are 21.25 grams in 500mL then there are 42.5 grams in a liter 42.5 grams = 42,500mg per liter =
   
   42,500 ppm

   Report (0) (0)  |   earlier  

3. Guest7596
   

   Since it's listing it in terms of grams, chances are that it is solid AgNO3. Since this is the case, you can probably just consider 500 mL as the final volume.

   Report (0) (0)  |   earlier  

4. Guest8387
   

   well 500mL is the final volume you can assume that adding silver nitrate doesn't change the volume because it is dissolved, i.e. lives in the intermolecular spaces of water, it actually dissociates into ions. So 500mL is the final volume.
   
   the mol wt of silver nitrate is :169.87
   
   # moles= mass/molecular weight
   
   = 21.25/169.87 =0.1258....
   
   Molarity is moles per L
   
   If 0.1258 moles are in 500 mL
   
   0.1258 * 2 are in 1000mL
   
   so the answer is 0.2517.... or 0.25M (2dp)

   Report (0) (0)  |   earlier