Aluminum vs. Salt

What can “eat” aluminum in seconds?

Safe­ty pre­cau­tions

Wear pro­tec­tive gloves, eye­wear, and a mask. Per­form this ex­per­i­ment in a well-ven­ti­lat­ed area.

Reagents and equip­ment

  • 50g cop­per(II) sul­fate pen­tahy­drate;
  • 100g sodi­um chlo­ride;
  • 100mL dis­tilled wa­ter;
  • a foil cup­cake lin­er;
  • a glass that fits the lin­er.

Step-by-step in­struc­tion

Set the cup­cake lin­er in the glass, then mea­sure 50g cop­per(II) sul­fate into it. Add 100mL dis­tilled wa­ter and 100g sodi­um chlo­ride. Watch as the so­lu­tion turns green. 5 min­utes lat­er, ob­serve the for­ma­tion of a red­dish-brown pre­cip­i­tate and rapid cor­ro­sion of the alu­minum lin­er.

Process de­scrip­tion

Alu­minum is an ac­tive met­al, but it is cov­ered with a strong ox­ide film and there­fore is quite in­ert. How­ev­er, in the pres­ence of sodi­um chlo­ride and cop­per(II) sul­fate, the ox­ide film is de­stroyed. This al­lows alu­minum to in­ter­act with the wa­ter mol­e­cules, re­leas­ing col­or­less hy­dro­gen gas:

2Al + 6H₂O = 2Al(OH)₃ + 3H₂

Alu­minum also dis­places cop­per ions from the so­lu­tion:

2Al + 3Cu²⁺ = 3Cu + 2Al³⁺