Equilibrium Composition

[Casey Collet 1I]

I'm having a hard time conceptually understanding why when you calculate the equilibrium composition the can product have a smaller value of moles than the moles required for the reactants to produce the reaction? Is it just the way in which the chemicals are bonding?

[Eduardo Torres 3G]

You may be thinking about the moles of molecules rather than the moles of atoms. The amount of moles of atoms on each side of the equation must be the same, but the same is not necessarily true for the number of molecules. For example, in the reaction H+ + I- --> HI, one can use 0.100 moles of H+ and 0.100 moles of I- to produce 0.100 moles of HI. Here, in a way, 0.200 moles of reactants are "being turned into" 0.100 moles of products, which seems like there is a net loss of moles but there are still 0.100 moles of H and 0.100 moles of I. Thus, event though the number of moles seems smaller, the reaction still follows the law of conservation of mass.