The reduction potential is an electrochemical concept. consider a substance that can exist in an oxidized form, x, and a reduced form, x - .a-such a pair is called a redox couple .b-the reduction potential of this couple can be determined by mea-suring the electromotive force generated by a sample half-cell connected to a stan-dard reference half-cell (figure 20.4 ).c-the sample half-cell consists of an electrode immersed in a solution of 1 m oxidant (x) and 1 m reductant (x - ).d-the standard reference half-cell consists of an electrode immersed in a 1 m h+ solution that is in equilibrium with h2 gas at 1 atmosphere (1 atm) of pressure. e-the electrodes are connected to a voltmeter, and an agar bridge allows the flow of ions between the half-cells. f-electrons then flow from one half-cell to the other through the wire connecting the two cells. if the reaction proceeds in the (pic)