The cell
has a potential of -0.2094 V when the solution in the right-hand compartment is a buffer of pH 4.006. The following potentials are obtained when the buffer is replaced with unknowns: (a) -0.2806 V and (b) -0.2132 V. Calculate the pH and the hydrogen ion activity of each unknown. (c) Assuming an uncertainty of 0.001 V in the junction potential, what is the range of hydrogen ion activities within which the true value might be expected to lie?