Answer : The correct option is, 0.21 moles
Solution : Given,
Molarity of the solution = 0.85 M = 0.85 mole/L
Volume of solution = 250 ml = 0.25 L 
Molarity : It is defined as the number of moles of solute present in one liter of the solution.
Formula used :

Now put all the given values in this formula, we get the moles of solute of the solution.


Therefore, the moles of solute is, 0.21 moles
Explanation:
TO calculate emperical formula , we need percentage composition of the elements and molecular mass of a specific compound which is already given in the question
then create a table with 1.name of element, 2.percentage given and its atomic mass , 3.no. of moles
( %given/at.mass of element) ... then take the least value in the no. of moles you have found now and divide with each no. of moles value .. to get a simple digit number.
You have got the empirical formula
Answer:
To avoid variation due to concentration
Explanation:
Hope this helps :)