Use the standard reduction potentials to determine what is observed at the cathode during the electrolysis of a 1.0 M solution of KBr that contains phenolphthalein.
`O_(2)(g) + 4H^(+)(aq) + 4e^(-) rightarrow 2H_(2)O(l)` `E^(@) = 1.23V`
`Br_(2)(l) + 2e^(-) rightarrow 2Br^(-)(aq)` `E^(@) = 1.07V`
`2H_(2)O(l) + 2e^(-) rightarrow H_(2)(g) + 2OH^(-)` `E^(@0 = -0.80V`
`K^(+) (aq) + e^(-) rightarrow K(s)` `E^(@) = -2.92V`
A. Solid metal forms.
B. Bubbles form and a pink colour appears.
C. Dark red `Br^(2)(aq)` forms.
D. Dark red `Br_(2)(aq)` forms.
