(b)
Let the oxidation state of Fe in ${Fe}_{3}O_{4}$ =$\ x$
$\therefore 3x + 4 \times ( - 2) = 0$
Or 3$x - 8 = 0$
$\therefore\ \ \ \ \ x = \frac{8}{3}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.