Which scientist proposed that energy of radiation is composed of extremely small indivisible packages called quanta? (quanta being the plural of quantum.) clinton davisson louis de broglie max planck sir isaac newton?

Explanation:

In late 1900s, the German physicist Max Planck studied the problem of black body radiation named the ultraviolet catastrophe:  the fact that the black bodies did not emit energy in all frequency ranges but at some specific energies.

Planck’s had to include the assumption that the electromagnetic energy could be emitted only in in discrete values, i.e. not in a continuos range, to work with his theory. These discrete values are tiny indivisible packages called quanta (the plural of quantum).

The energy, E, radiated from a black body could only be a multiple of an elementary unit, which is the Planck constant:

Where:

This is the start of the quantum theory: the matter is discontinuous in nature.

Nevertheless, for Planck, quanta were only an idealization and it was Albert Einstein (early 1900s) who ended showing the existence of quanta (photons).

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.