Douglasite is a mineral with the formula 2kcl # fecl2 # 2h2o. calculate the mass percent of douglasite in a 455.0-mg sample if it took 37.20 ml of a 0.1000-m agno3 solution to precipitate all the cl2 as agcl.

Answer : The mass percent of Douglasite is 63.75 %

Explanation :

First we have to calculate the moles of .

As we know that,

Moles of = Moles of AgCl = Moles of =

The formula of Douglasite is,

The molar mass of Douglasite = 311.88 g/mole

Now we have to calculate the moles of atoms.

In the formula of Douglasite, there are 4 atoms.

Now we have to calculate the mass of Douglasite.

conversion used : (1 g = 1000 mg)

Now we have to calculate the mass percent of Douglasite.

Therefore, the mass percent of Douglasite is 63.75 %

"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o  

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles  

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles  

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1  

0.44 / 0.09 = 4.8  

mgco3-5h2o"

it means there are 3 atoms of oxygen