Arrange Cu, Ca, Al, Fe, Mg, Pb, Na and Zn in the decreasing order, in which they appear in the activity series;

Question

(i) Arrange Cu, Ca, Al, Fe, Mg, Pb, Na and Zn in the decreasing order, in which they appear in the activity series; putting down the most reactive metal first and least reactive in the last. 

(ii) (a) Among the above metals, write the names of metals which will displace hydrogen from water or steam. 

(b) Give two evidences to show that magnesium is more reactive than iron

Answer 1

 (i) The given metals are arranged in the activity series of metals as follows: Na, Ca, Mg, Al, Zn, Fe, Pb (most reactive) and Cu (least reactive) 

(ii) (a) (1) Sodium and calcium displace hydrogen from cold water. 

2Na + 2H₂O ⟶ 2NaOH + H₂ ↑

Ca + 2H2O ⟶ Ca(OH)₂ + H₂↑

(2) Magnesium and zinc metals are less reactive as they react with boiling water to liberate hydrogen gas.

Mg + 2H₂O ⟶ Mg(OH)₂ + H₂↑

Zn + 2H₂O ⟶ Zn(OH)₂ + H₂↑

(3) Iron which is less reactive, reacts in red hot conditions with steam to liberate hydrogen gas.

3Fe + 4H₂O ⟶ Fe3O₄ + 4H₂↑

(4) Lead and copper almost fail to liberate hydrogen gas in any conditions, because they are not so reactive. They lie just above and below hydrogen in activity series of metals. 

(b) (1) Magnesium reacts with boiling water to liberate hydrogen gas, while iron can do so with steam in red hot condition only. 

(2) Magnesium can displace hydrogen from acids vigorously in cold but iron displaces hydrogen slowly.