What is the molarity of a solution prepared by mixing 12.5g FeCl3 in enough water to make 500mL of solution/

Answer 1

Hello, Priya,

Molarity is defined as moles per liter. A 1 Molar solution has 1 mole of the element/compound in 1 liter of solution. Note that it is the ratio that counts. 1 Molar can also mean 0.5 moles in 0.5 liters.

In this case, calculate the number of moles contained in 12.5 g of FeCl₃. The molar mass of FeCl₃ is 162.2 g/mole. Divide the mass of FeCl₃ by the molar mass to get moles {Use the units to see why you divide: g/(g/mole) results in the grams canceling and mole moving to the top].

Now that you have the number of moles (it should be well less than 1 since you only have 12.5 g). Take the number of moles and divide by 0.5 liter. That will give you the answer, since we now have moles/liter, the definition of Molar.

Bob