# Which of the following pairs will give displacement reactions? (a) NaCl solution and copper metal (b) $$MgCl_2$$ solution and aluminium metal (c) $$FeSO_4$$ solution and silver metal (d)$$AgNO_3$$ solution and copper metal.

To solve this question, we should first remember the definition of displacement reaction which states that those reactions where a more reactive element displaces/removes a less reactive element is called displacement reaction. Now let's look at each option one by one.

(a) NaCl solution and copper metal - In order for this reaction to complete copper(Cu) must replace Na(sodium) but this is not possible as copper is less reactive than sodium(see reactivity series)

(b)$$MgCl_2$$ solution and aluminium metal - Here, aluminium(Al) must replace magnesium(Mg) but it is not possible as aluminium(Al) is less reactive than magnesium(Mg)

(c)$$FeSO_4$$ solution and silver metal -Here, Ag(Silver) must replace Fe(Iron) but it is not possible

(d) $$AgNO_3$$ solution and copper metal - Yes, this reaction is possible as copper(Cu) is more reactive than silver(Ag) so, cu(copper) metal will easily displace Ag and reaction will be

$$AgNO_3 + Cu \Rightarrow Cu(NO_3)_2 +Ag$$