What does a negative value for a standard potential indicate? PLEASE HELP!!
The negative values mean the half reaction is less likely to occur spontaneously as written.
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A negative value for the standard potential indicates that the reaction is not spontaneous under standard conditions. In other words, it suggests that the reaction proceeds less readily or requires an input of energy to occur.
To determine the standard potential for a reaction, you need to consult a table of standard reduction potentials. This table lists the standard reduction potentials for various half-reactions. The standard reduction potential is a measure of the tendency of a species to gain electrons and undergo reduction.
To understand why a negative standard potential indicates non-spontaneity, consider the equation for calculating the cell potential (E° cell) of a galvanic cell:
E° cell = E° cathode - E° anode
The standard potential of the cathode (reduction half-reaction) is subtracted from the standard potential of the anode (oxidation half-reaction). If the result is positive, the reaction is spontaneous in the direction written. However, if the result is negative, the reaction will not proceed spontaneously and requires an external energy source to drive the reaction.
In summary, a negative value for the standard potential indicates a non-spontaneous reaction under standard conditions. To determine the standard potential, consult a table of standard reduction potentials and use the equation for calculating the cell potential.