Which statement is true for all equilibrium systems?
a. the mass of the reactants is equal to the mass of the products.
b. the addition of a catalyst changes the equilibrium concentrations.
c. the concentration of the reactants is equal to the concentration of the products.
d. heating the system always favors the exothermic reaction.
e. the rate of the forward reaction is equal to the rate of the reverse reaction.

metals are good conductor of electricity. it has free electrons on their surface. according to electron pool theory, each atom present in a metal crystal losses all of its valence electron and as a result a pool of free is form. these pool of electrons are free to move and   conduct electricity easily   while making metal as good conductor.

the correct answer is a. the ability of electrons to flow throughout the metal.

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