Question

The standard electrode potentials of $$Zn$$ and $$Ni$$ respectively are $$-0.76V$$ and$$-0.25V$$,Then the standard emf of the spontaneous cell by coupling these under standard conditions is:
A) $$+1.01V$$
B) $$-0.51V$$
C) $$+0.82V$$
D) $$+0.25V$$
E) $$+0.51V$$

Answer 1

Hint: Standard Electrode Potentials is genuinely difficult to gauge the potential of a single electrode: just the contrast between the potentials of two terminals can be estimated. We can, in any case, think about the standard cell potentials for two distinctive galvanic cells that share one sort of electrode for all intents and purposes.

Complete step by step answer:
Standard terminal potential ($$E^{\circ }$$) in electrochemistry is characterized as the proportion of the individual potential of a reversible electrode at standard state with particles at a powerful convergence of $$1mold{m}^{-3}$$ at the pressure of $$1atm$$.
The cathode potentials of metals given above assist us with understanding the simplicity of a metal to get oxidized or diminished. With this we can choose the anode and cathode terminals. Oxidation happens at anode and decrease at cathode, so pick the terminals that fulfill the necessities of the individual terminals.
Electrochemistry is the part of actual science that essentially manages the connection among power and recognizable compound change. Electrochemical response is a synthetic response wherein current is remotely provided or delivered through an unconstrained substance response. Substance responses where electrons are straightforwardly moved between the constituent particles or molecules are called oxidation-decrease or rather redox responses.
All in all, we can say that a response is unconstrained when the emf of the cell is positive. It shows that the cell response is doable and, in this way, happens. In the electrochemical arrangement the request for components is $$Zn>Fe>Ni$$ regarding simplicity of oxidation. Thus, the cell is possible when $$Zn$$ is anode and either $$Fe$$ or $$Ni$$ is cathode
The standard anode potential of $$Zn$$( $$E_{anode}^o$$)$$=-0.76V$$
The standard anode potential of $$Ni$$ ($$E_{cathode}^o$$) $$=-0.25$$
For spontaneous reaction Ecell ought to be positive.
Along these lines, the response ought to be:
$$Zn\left(s\right)+N{i}^{2+}\left(aq\right)\to Z{n}^{2+}\left(aq\right)+Ni\left(s\right)$$
$$E_{cell}^o=E_{\left(cathode\right)}^o-E_{\left(anode\right)}^o$$
$$=-0.25-\left(-0.76\right)=+0.51V$$
So, the correct option is ($$E$$).

Note:
The standard cell potential ($$E_{cell}^o$$) is accordingly the distinction between the organized decrease potentials of the two half-responses, not their total:
$$E_{cell}^o=E_{\left(cathode\right)}^o-E_{\left(anode\right)}^o$$
$$\mathrm{\Delta }G{}_{cell}^{\circ }=-nFE{}_{cell}^{\circ }$$(For Gibbs free energy).