The isomerization of methylisonitrile to acetonitrile (CH3NC(g) CH3CN) is first order in CH3NC. The rate constant for the reaction is 9.45 x 10-5 s-1 at 478 K. What is the half-life of the reaction when the initial concentration of CH3NC is 0.0300 M?

The half life is    

Explanation:

   The half life of a first order  reaction is mathematically represented as

 Substituting    for the rate constant

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.