Hello!
Molarity is defined as the number of moles of a substance that can be found in 1 liter of solution. That is expressed mathematically as M=mol/L
For the FeCl₃ solution:
[tex]M= \frac{mol FeCl_3}{L sol}= \frac{0,34 moles FeCl_3}{0,45 L}= 0,756 M[/tex]
So, the concentration of this solution is 0,756 M
Have a nice day!