2. Compare the following terms: a. an otom and a molecule
b. an atom and an ion
c. a cation and an anion

a.

Atoms are the building blocks of matter. Molecules are group of two or more atoms bonded together.

b.

Atoms are neutral; they contain the same number of protons as electrons. An ion is an atom or molecule that has a different number of electrons than protons, so it has a charge.

c.

Cations are positively charged ions. Anions are negatively charged ions.

it is called acid bonding

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.