Which of the following solutions cannot be used in a salt bridge?

When a lead storage battery is discharged,

In $H_2-O_2$ fuel cell,the reaction occurring at the cathode is:

Explain the construction of a galvanic cell based on the Daniell cell. In a galvanic cell,explain the positive and negative electrodes with suitable chemical reactions.

Which one of the following processes is non-spontaneous?

$Cu^{+}_{(aq)}$ is unstable in solution and undergoes simultaneous oxidation and reduction,according to the reaction $2 Cu^{+}_{(aq)} \rightleftharpoons Cu^{2+}_{(aq)} + Cu_{(s)}$. Choose the correct $E^{\circ}$ for the above reaction if $E^{\circ}_{Cu^{2+}/Cu} = 0.34 \ V$ and $E^{\circ}_{Cu^{2+}/Cu^{+}} = 0.15 \ V$.