The procedure for an experiment is
a. the variable that you will change
b. a set of safety rules that you need to follow in the lab
c. what you're going to do and how you're going to do it
d. research you've done about the topic you're investigating

 The correct answer is: C. what you're going to do and how you're going to do it

Explanation:  A good experiment should follow a design with a few logical steps. An experiment must be carried out methodically in order to perform valid and reliable measurements. Experimenting is a procedure to check one or several hypotheses about a specific topic.

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.