‘by using displacement reactions it is possible to deduce the order of reactivity of the halogens.’
discuss this statement with reference to the elements bromine, iodine and chlorine only.

Explanation:

The halogens have seven electrons in their outermost shell. Each halogen atom lacks a single electron to make their octet a complete one. Elements in the halogen group are univalent and also acceptors of electrons. They are all non-metals and oxidizing agents. The oxidizing power of the halogens decreases from top to down the group. This is why the more powerful halogens displaces a less powerful one from simple salts.

         Cl₂ + 2KBr → 2KCl + Br₂

         Cl₂ + 2KI → 2KCl + I₂

          Br₂ + 2KI → 2KBr + I₂

          I₂ + 2KCl → No reaction

n2(g) + 3h2-> 2nh3(g)   this is the balanced equation

note the mole ratio between n2, h2 and nh3.   it is 1 : 3 : 2   this will be important.

moles n2 present = 28.0 g n2 x 1 mole n2/28 g = 1 mole n2 present

moles h2 present = 25.0 g h2 x 1 mole h2/2 g = 12.5 moles h2 present

based on mole ratio, n2 is limiting in this situation because there is more than enough h2 but not enough n2.

moles nh3 that can be produced = 1 mole n2 x 2 moles nh3/mole n2 = 2 moles nh3 can be produced

grams of nh3 that can be produced = 2 moles nh3 x 17 g/mole = 34 grams of nh3 can be produced

note:   the key to this problem is recognizing that n2 is limiting, and therefore limits how much nh3 can be produced.

d: the voltage of the secondary coil is less than that of the primary coil.

im not suree sorry if wrong