Question

Burning magnesium ribbon in the air to form magnesium oxide is an example of ___ (combination or decomposition) reaction.

Answer 1

Magnesium ribbons burn in air to form magnesium oxide and. Both magnesium and oxygen combine together to form magnesium oxide which is a white powder.

Complete step by step answer:
A combination reaction is a type of reaction in which two or more elements or compounds combine to form a single compound as in this reaction oxygen and magnesium combine to a white powder which is magnesium oxide. Magnesium oxide gives two electrons to oxygen which leads to the formation of this white powder.
Oxygen and many of the halogens both are very reactive and they undergo disproportionation reactions. Even aluminium and oxygen also combine with each other to form aluminium oxide which is an example of combination reaction.
Burning magnesium ribbon in the air to form magnesium oxide is an example of combination reaction.
The reaction followed is:
Magnesium combine with oxygen and form magnesium oxide and energy
$Mg+{{O}_{2}}\to MgO$
Balanced chemical reaction:
$2Mg+{{O}_{2}}\to 2MgO$
A disproportionation reaction is a type of reaction in which one compound breaks into two compounds one having high oxidation state and one having low oxidation state. Examples of disproportionation reaction is disproportionation of hydrogen peroxide to water and oxygen.
Hence the correct answer combination reaction i.e. Burning magnesium ribbon in the air to form magnesium oxide is an example of combination reaction.

Note: In order to start the burning of magnesium ribbon it requires a source of energy, the flame provides a source of heat which acts as a source of energy. Activation energy is the minimum energy required for the completion of a chemical reaction.