P12-16B The elementary reversible liquid-phase reactiontakes place in a CSTR with a heat exchanger. Pure A enters the reactor.(a) Derive an expression (or set of expressions) to calculate G(T) as a function of the heat of reaction, equilibrium constant, temperature, and so on. Show a sample calculation for G(T) at T = 400 K.(b) What are the steady-state temperatures? (Ans.: 310, 377, 418 K.)(c) Which steady states are locally stable?(d) What is the conversion corresponding to the upper steady state?(e) Vary the ambient temperature Ta and make a plot of the reactor temperature as a function of Ta, identifying the ignition and extinction temperatures.(f) If the heat exchanger in the reactor suddenly fails (i. e., UA = 0), what would be the conversion and the reactor temperature when the new upper steady state is reached? (Ans.: 431 K.)

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.

the answer is b because, investigating whether another species of moth also drinks tears might be interesting, but it would not directly explain why this species of moth does.

to explain why this species of moth drinks tears, the scientist could ask: "what nutrients that moths need are in elephant tears? "

the scientist could experiment with moth repellent or oter ways to keep the moths away, but that would not answer his original question.