Formation of Hydrogen Gas: The
Rate Of a Reaction
The rates of reaction between a strong acid
and magnesium metal, and a weak acid and
magnesium metal to generate hydrogen gas
are compared.
Purpose
• In flask number one was added HCl (strong acid) and in
flask number two was added CH3COOH (weak acid) in
equal amounts to both flasks. Magnesium metal was then
added to each flask which was covered immediately with a
balloon. The reaction between the acid and the metal
produced hydrogen gas.
Demonstration
• Flask number two with the strong acid
inflated the balloon much faster than flask
number one with the weak acid.
Concepts
• Acids
• Oxidation of metals
• Hydrogen
Acids
• An acid is a substance that is able to donate a proton and
increase the concentration of ions when it dissolves in
water.
• A strong acid is an acid that ionizes completely in water.
• The most common strong acids are HCl, HBr, HI, HClO3,
HClO4, H2SO4 and HNO3.
• A weak ccid is an acid that partially ionizes in water.
• Many weak acids are organic compounds that are made of
carbon, hydrogen and opxygen.
• Acetic acid is an organic compound that is found in
vinegar.
• Acetic acid has the chemical formula CH3COOH
Oxidation of Metals
• Oxidation is a process in which a substance loses one or
more electrons.
• In this demonstration the metal is been oxidized by the
acid to make a salt and hydrogen gas.
• Mg(s) + 2HCl(aq)  MgCl2(aq) + H(g)
• Mg(s) + CH3COOH(aq)  Mg(CH3COO)2(aq) + H2(g)
• A piece of iron rusting is a good example of oxidation of a
metal.
Hydrogen
• Hydrogen is the most abundant element in the
universe.
• It is the first element in the periodic table and has
the lowest atomic weight of 1.006.
• At room temperature it is a colorless and odorless
gas.
• Hydrogen gas exists as a diatomic molecule, H2
Conclusions
• Stronger acids generate hydrogen gas faster because they
are able to donate protons at a faster rate. This is in
keeping with the definition and classification of strong
acids. Acetic acid, a weak acid, does not react as quickly
as a strong acid.
Comments
• The oxidation of metals is used when small amounts of
hydrogen are needed in the laboratory.
• For industrial use some other methods are use like reacting
methane(natural gas) with steam at 1100C.