3TV - Chapter 4 - Section 4.2 - Decomposition

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• Middelbare school
• vwo
• Leerjaar 3

4.2 Decomposition

Heating substances, what can happen:

• Phase transition 
• Separation 
• Combustion
• Chemical reaction, e.g. Decomposition

Decomposition

• Chemical reaction with only one reactant
                                            (so no oxygen or other substance!).
• Two or more products (Can be elements or other compounds) 

Chemical reaction

Reactant --> decomposition products

Decomposition

1 reactant

2 or more products

Reactant = a compound

Combustion

2 reactants

1 or more products

Reactant = Fuel + O2

Energy effect of decomposition reactions.

Most decomposition reactions are endothermic.

So reaction stops when you stop adding energy 

Three types of decomposition

• Thermolysis (with heat)

In next slide a video with an example: decomposition of sugar

Electrolysis

decomposing using electricity

Three types of decomposition

• Thermolysis (with heat)
• Electrolysis (with electricity)
• Photolysis (with light)

Photolysis

decompsition using light

equation for decomposition of

Always one reactant 

silver chloride ( AgCl )

Two examples of exothermic decomposition reactions:

* decompostion of ammonium dichromate

Decomposition of Ammonium nitrate

2 NH₄NO₃ (s) —> 2 N₂ (g) + 4 H₂O(g) + O₂ (g)

Three types of decomposition

• Thermolysis (with heat)
• Electrolysis (with electricity)
• Photolysis  (with light)

Because the thermolysis is sometimes mixed up with combustion this requires some extra focus.

During the ironing of a shirt with an iron which is too hot there form scorchmarks. This is a ...

1. Thermolysis
2. Electrolysis
3. Photolysis
4. No decomposition

A couple of years after installation a brightly coloured curtain has become faded in colour. This happened due to ...

1. Thermolysis
2. Electrolysis
3. Photolysis
4. No decomposition

When you heat up glass to a really high temperature you can shape it into another form, this is ...

1. Thermolysis
2. Combustion, No decomposition
3. Photolysis
4. Phase change, No decomposition

With the help of electicity aluminium is made from bauxite ore. This is ...

1. Thermolysis
2. Electrolysis
3. Photolysis
4. No decomposition

During an endothermic reaction ...

1. energy is released
2. energy is needed at the beginning
3. energy is needed during the reaction

What kind of reaction is:

CuCO​3​​(s)−>CuO(s)+CO​2​​(g)

1. Combustion
2. Decomposition

Most decomposition reactions requiers energy continuously. How do we call this kind of reaction?

1. Exothermic reaction
2. Energy-effect
3. Endothermic reaction

Sulfer chloride is seperated in sulfer and chloride with the help of the sun.

Which one?

1. Thermal decomposition
2. Electrolysis
3. Photolysis

Water is turned into hydrogen and oxygen when by electric current passing trough.

Which type of decomposition is it?

1. Thermal decomposition
2. Electrolysis
3. Photolysis