Which of the following observations indicates that an atom has neutrons?
a. some uncharged particles are scattered by a beryllium atom when it hits a gold foil.
b. some uncharged particles bounce back from a gold foil when it is bombarded with alpha particles.
c. a radiation with neutral particles is emitted when alpha particles strike beryllium atoms.
d. a radiation which attracts electrons is produced when a beryllium atom is bombarded with alpha particles.

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.

the answers are

c and c