(PLEASE ANSWER ASAP) What is defined as the energy required to start a chemical reaction?

A:precipitate energy

B:heat

C:reactant energy

D:activation energy

Option D. Activation energy

Explanation:

Activation energy is the minimum energy required to start a chemical reaction. For a reaction to occur, the reactants must possess energy equal or greater than the activation energy else the reaction will not occur.

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.

fe 55.85 g/mol and h2o 18.02 g/mol.