Calculate δh∘ in kilojoules for the reaction of ammonia nh3 (δh∘f=−46.1kj/mol) with o2 to yield nitric oxide (no) (δh∘f=91.3 kj/mol) and h2o(g) (δh∘f=−241.8kj/mol), a step in the ostwald process for the commercial production of nitric acid.

4nh3(g)+5o2(g)→4no(g)+6h2o(g)

for the given reaction is -901.2 kJ.

Explanation: Enthalpy of the reaction is the amount of heat released or absorbed in a given chemical reaction.

Mathematically,

For  given reaction:

Putting values in above equation, we get:

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.