To calculate the power output of an electrochemical cell, we can use the formula:Power P = Voltage V Current I Given the standard potential voltage of the cell is +0.34 V and the current flowing through it is 2.5 A, we can calculate the power output as follows:P = 0.34 V 2.5 AP = 0.85 W watts Now, we need to find the total energy output over the 3-hour period. We can do this by using the formula:Energy E = Power P Time t First, we need to convert the time from hours to seconds:3 hours 60 minutes/hour 60 seconds/minute = 10,800 secondsNow, we can calculate the total energy output:E = 0.85 W 10,800 sE = 9,180 J joules So, the power output of the electrochemical cell is 0.85 W, and the total energy output over the 3-hour period is 9,180 J.