Which of the following alone is not evidence of a chemical change?

a. color change

b. fizzing observed

c. melting

d. rusting

C. melting

Explanation:

Color Change shows a chemical reaction occurred as something new was formed. Fizzing is the release/production of gas. Rusting is an oxidation which converts metal into rust. Melting is a change in state, think ice melting into liquid water, the water is still the same substance.

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.