The question is incomplete, here is the complete question:
A chemist prepares a solution of iron (III) bromide
by measuring out 2.78 g of iron (III) bromide into a 50. mL volumetric flask and filling the flask to the mark with water.
Calculate the concentration in mmol/L of the chemists iron (III) bromide solution. Be sure your answer has the correct number of significant digits.
<u>Answer:</u> The concentration of iron(III) bromide solution is 0.19 M
<u>Explanation:</u>
To calculate the molarity of solution, we use the equation:

We are given:
Given mass of iron(III) bromide = 2.78 g
Molar mass of iron(III) bromide = 298.6 g/mol
Volume of solution = 50. mL
Putting values in above equation, we get:

Hence, the concentration of iron(III) bromide solution is 0.19 M