A pH indicator works in a better way in a range of pH = pKa ± 1. That means we need to determine the pKa of the indicator propyl red to find the range over which it change its color. That is:
pKa = -log Ka
pKa = -log 3.3x10⁻⁶
pKa = 5.48
That means the range over propyl red will change from yellow to red or vice versa is:
W*V i believe because it comes down to this : I is the current, W is wattage V is volts and the * is the thing that represents the Amperes (i’m not 100% but this is my best)
