Answer: 0.174 g
Step-by-step explanation:
First of all understand that charge on an atom like here 2+ will not vary molar mass. because ions are formed by loss or gain of electrons and electrons do not contribute to the mass of an atom or ion. so losing or gaining electron doesnt create any difference.
molar mass of Fe, i.e. mass of 1 mole of Fe is 56 g. So, mass of 1 mole of Fe2+ will also be 56 g.
given is 0.003109 moles of Fe2+,
Use maths,
1 mole of Fe2+ weighs 56 g
So, 0.003109 moles will weigh = (56 g / 1 mol ) x 0.003109 = 0.174 g.