How do substances and mixtures The composition of one is always the same, and the composition of the other varies
One contains only one type of atom, and the other contains two or more
One is always homogeneous, and the other is always heterogeneous
One contains one type of molecule, and the other contains two types
it for 100 points please give it correctly.

hello hope this helps :)

a pure substance consists only of one element or one compound. a mixture consists of two or more different substances, not chemically joined together.

Explanation:

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.