Collapsing Can
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Transcript Collapsing Can
Preparation of Oxygen
Gas from Bleach
When bleach is treated with a catalyst the rapid
evolution of oxygen gas ensues
Demonstration
The commercial bleach was a solution of
sodium hypochlorite in water
NaClO(aq)
When treated with a small amount of
cobalt(II)chloride the hypochlorite
decomposed Catalyst
2ClO- (aq)
O2(g) + 2Cl-(aq)
The bubbles given off were the oxygen
gas as concluded from
Pine splint test
Purpose
To use a catalyst to decompose
bleach
To collect the decomposition
product
To test for the presence of oxygen
gas
Concepts
1.
Decomposition Reactions
2.
Catalysts
3.
Collection and Determination of
Oxygen
1. Decomposition Reactions
Decomposition reactions are of the
kind
A-B
A
+
B
In decomposition reactions, a
single substance is converted to
more than one new substance
In this demonstration hypochlorite
ion decomposes into oxygen gas
and chloride ion
2. Catalysts
A catalyst is a substance which enables
a chemical change to occur
A catalyst assists the reactants to
convert to products
The catalyst itself may be used over and
over: It itself is not changed
When a catalyst is present it is written
over the reaction arrow
Addition of a catalyst will speed the rate
of many chemical reactions allowing
them to occur faster than they otherwise
would
3. Collection and Determination
of Oxygen
Oxygen is a gas and is conveniently
collected by the displacement of water
A glowing--but not burning--pine splint
will burst into flame if oxygen gas is
present
Conclusions
Oxygen gas was a decomposition
product of bleach
A catalyst was used to cause rapid
decomposition
Oxygen was easily collected
Oxygen supported combustion
reactions
with a glowing pine splint
Comments
This reaction is not only a
decomposition, but also a redox
reaction
Bleach should NEVER be mixed
with any household chemicals!!!