Answer : The correct option is, (b) 22.1 g
Solution : Given,
Mass of iron = 15.5 g
Molar mass of iron = 56 g/mole
Molar mass of
= 160 g/mole
First we have to calculate the moles of iron.

Now we have to calculate the moles of
.
The balanced reaction is,

From the balanced reaction, we conclude that
As, 2 moles of iron obtained from 1 mole of 
So, 0.276 moles of iron obtained from
mole of 
Now we have to calculate the mass of 

Therefore, the amount of
required are, 22.1 grams.