Consider the equation. Which represents the correct mass-volume relationship at STP?
32.00 g of O2 react with an excess of H2 to produce (2 ´ 22.4) L of H2O.
2.00 g of H2 react with an excess of O2 to produce (2 ´ 22.4) L of H2O.
32.00 g of O2 react with an excess of H2 to produce 22.4 L of H2O.
(2 ´ 2.00) g of H2 react with an excess of O2 to produce 22.4 L of H2O.

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.

use quiz let it tells you all the answers thats what i use