Question
Zinc liberates hydrogen from dilute hydrochloric acid, copper fails to do so. Explain.
Solution
We know zinc has negative reduction potential [E° (Zn2+1 Zn) = –0 . 76V] and lies above hydrogen in the electrochemical series. Therefore, the electron accepting tendency of zinc is less than that of hydrogen or its electron releasing tendency is more.
Thus, zinc can lose electrons to H+ ions of the acid and as a result, hydrogen gas is liberated.
Since copper has a positive reduction potential (E° = +0.34 V) and lies below hydrogen in the electrochemical series, therefore, it cannot lose an electron to H+ ions of the acid. Hence H2 gas is not liberated.
