Which statement about enthalpy is true?

the enthalpy of formation for a pure element in its standard state is always positive.
the enthalpy of formation for a pure element in its standard state is always negative.
enthalpy is a state function because its change depends only on initial and final conditions.
enthalpy is not a state function because its change depends on the identities of the reactants and products.

Answer : Option C) Enthalpy is a state function because its change depends only on initial and final conditions.

Explanation : Enthalpy can be defined as a thermodynamic quantity which is equivalent to the total heat content of a system. It is equal to the internal energy of the system(U) plus the product of pressure and volume (PV).

E = U + PV ;

It is a state function as it only depends on the initial and final conditions, and not on the path taken to reach these reaction conditions.

Therefore, the integral of state functions can be taken using only two values: the final and initial values.

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.