Can carbon and hydrogen form double bonds between them?

Carbon has four valence electrons, so it can achieve a full outer energy level by forming four covalent bonds. When it bonds only with hydrogen, it forms compounds called hydrocarbons. Carbon can form single, double, or triple covalent bonds with other carbon atoms.

The carbon-hydrogen bond (C–H bond) is a bond between carbon and hydrogen atoms that can be found in many organic compounds. This bond is a covalent bond meaning that carbon shares its outer valence electrons with up to four hydrogens. This completes both of their outer shells making them stable.

^Hope it helps, Hazel^

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.