How was Nikolay Nikolaevich Semenov awarded the Noble Prize?

Name: Nikolay Nikolaevich Semenov 
Country: Russian
Date of Birth: April 15, 1896
Date of Death: September 25, 1986
The subject of Study: Chain reaction, reaction mechanism, reaction rate
Noble Prize Year: Nobel Prize for Chemistry in 1956 for research in chemical kinetics.
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