Relating cause and effect. A chemistry student decided to weigh a bag of microwave popcorn before and after popping it. She opened the bag after microwaving it to let steam escape and then weighed it again. She noticed that the mass of the unpopped popcorn was 0.5g more than the mass of the popped popcorn. Was the matter destroyed when the popcorn popped? Explain your answer.

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.

yes the answer is total mass in unchanged   : )