• Activity for the students
Experience
The reaction between Magnesium and Hydrochloric Acid
Aim: To investigate the reaction between magnesium and hydrochloric acid. The more concentrated the acid is, the
faster the magnesium ribbon will dissolve. This is because the rate of reaction depends on how frequently the
molecules of the reacting substances collide. A more concentrated substance has more molecules for a given volume
than a more dilute substance. Because there are more molecules about, the frequency of successful collisions is
greater, and the reactions happen faster.
Discussion
This demonstration can be used to illustrate the characteristic reaction of metals with acid, a single replacement
reaction, or to demonstrate the generation of hydrogen gas. The flammability of hydrogen gas can be demonstrated by
carefully holding a match or fireplace lighter up to the popping hydrogen bubbles. An audible crackling sound is heard
as the hydrogen burns.
Materials
Petri dish
1cm strip of magnesium ribbon
wash bottle containing 1M HCl
forceps
overhead projector
Procedure
Place the Petri dish on the overhead projector. Pour hydrochloric acid into the Petri dish to a depth of about 5mm. Turn
on the projector and focus it. Using forceps, place the magnesium ribbon into the Petri dish. The magnesium reacts
with the acid, producing visible bubbles of hydrogen gas.
Safety Precautions
Magnesium ribbon is a flammable solid. Hydrochloric acid is a corrosive liquid. Hydrogen gas is explosive. However,
the very small quantities and low dilutions used in or produced by this demo present little hazard. Wear safety goggles.
Keep flammables and open flame away from the vicinity.
20