Final answer:
The slope of the standard cell potential plot versus temperature indicates the reaction's entropy change, while the y-intercept reflects the standard cell potential, which indicates if the reaction is spontaneous and relates to the reaction's enthalpy change.
Step-by-step explanation:
When measuring the standard cell potential at different temperatures, and you obtain a plot that is a straight line, the slope and y-intercept of this line can give you valuable information about the chemical reaction in question. The slope of the line relates to the temperature dependence of the reaction, specifically to the changes in the entropy (ΔS) of the system. This relationship is described by the Nernst equation. According to this equation, the slope should be equal to -ΔS/R (R is the gas constant). The y-intercept, on the other hand, provides the standard cell potential (Eºcell) when extrapolated to 1/T = 0, which according to the Gibbs-Helmholtz equation, corresponds to the enthalpy change (ΔH) of the reaction. Therefore, from the y-intercept, one can compute the standard cell potential at a fixed temperature, usually 25°C which indicates whether the reaction is spontaneous (positive value for the standard cell potential) under standard state conditions.