Mole ratio is the ratio between the amount in moles of any two compounds involved in a chemical reaction
3
the mole of Fe3O4 is 1 mole while that of Fe is 3 moles from the reacting equation below
Fe + 4 H2O ----> Fe3O4 + 4 H2
therefore the mole ratio of Fe3O4 to Fe is 1:3(answer A)
The differential rate expression for the rate of change in the concentration of B with time is
-rB = dCB/dt = kCB^n
where k is the rate constant and
n is the order of the reaction
This is assuming that the rate is only affected by the concentration of B and the order of the reaction is in the nth order.
Br2(i) would be sealed due to my calculations