Which compound acts as an oxidising agent in a dry cell?

The following four solutions are kept in separate beakers and copper metal is put in each of them. Which solution will become blue after some time?

Which of the following will be able to react with dilute $HCl$ to give hydrogen gas?

Consider the figure and answer the questions $(i)$ to $(vi)$ given below.
$(i)$ Redraw the diagram to show the direction of electron flow.
$(ii)$ Is the silver plate the anode or cathode?
$(iii)$ What will happen if the salt bridge is removed?
$(iv)$ When will the cell stop functioning?
$(v)$ How will the concentration of $Zn^{2+}$ ions and $Ag^{+}$ ions be affected when the cell functions?
$(vi)$ How will the concentration of $Zn^{2+}$ ions and $Ag^{+}$ ions be affected after the cell becomes 'dead'?

The electrode reaction that takes place at the anode of a $CH_4-O_2$ fuel cell is?

Depict the galvanic cell in which the reaction $Zn_{(s)} + 2Ag^{+}_{(aq)} \rightarrow Zn^{2+}_{(aq)} + 2Ag_{(s)}$ takes place. Further show:
$(i)$ Which of the electrode is negatively charged?
$(ii)$ The carriers of the current in the cell.
$(iii)$ Individual reaction at each electrode.