$A$ cell reaction is spontaneous when

Which among the following is an example of a metal-metal ion electrode?

Colourless solutions of the following four salts are placed separately in four different test tubes and a strip of copper is dipped in each one of these. Which solution will turn Blue?

In the experiment set up for the measurement of $EMF$ of a half-cell using a reference electrode and a salt bridge,when the salt bridge is removed,the voltage

Which of the following reactions is used to make a fuel cell?

In a hydrogen-oxygen fuel cell,the combustion of hydrogen occurs to: