Question

Activity series of metals with dilute hydrochloric acid is ______

• A. $Mg>Al>Zn>Fe$
• B. $Fe>Zn>Al>Mg$
• C. $Al>Zn>Fe>Mg$
• D. $Zn>Fe>Mg>Al$

Answer 1

The correct option is A

$\mathrm{Mg}>\mathrm{Al}>\mathrm{Zn}>\mathrm{Fe}$

The explanation for correct option A:

• Arrangement of the metals on the basis of their reactivity towards other elements is termed as activity series. The activity series in decreasing order is:

$\mathrm{K}>\mathrm{Na}>\mathrm{Li}>\mathrm{Ba}>\mathrm{Sr}>\mathrm{Ca}>\mathrm{Mg}>\mathrm{Al}>\mathrm{Mn}>\mathrm{Zn}>\mathrm{Cr}>\mathrm{Fe}>\mathrm{Cd}>\mathrm{Co}>\mathrm{Ni}>\mathrm{Sn}>\mathrm{Pb}>\mathrm{H}>\mathrm{Sb}>\mathrm{Bi}>\mathrm{Cu}>\mathrm{Hg}>\mathrm{Ag}>\mathrm{Au}>\mathrm{Pt}$

• Elements at the starting of this series are comparatively more reactive than elements present after them in the series.
• In a single displacement reaction, an element from its compound is substituted by another element to form two product molecules. Elements that are more reactive according to the activity series can displace the elements less reactive than them from their compounds.
• In the reaction between metal and Hydrogen chloride or Hydrochloric acid $\left(\mathrm{HCl}\right)$, metal displaces Hydrogen $\left(\mathrm{H}\right)$ from Hydrochloric acid and forms metal chloride and Hydrogen molecule $\left({\mathrm{H}}_2\right)$.
• According to the activity series, Magnesium $\left(\mathrm{Mg}\right)$ is most reactive followed by Aluminium $\left(\mathrm{Al}\right)$, Zinc $\left(\mathrm{Zn}\right)$ and Iron $\left(\mathrm{Fe}\right)$. Therefore, Magnesium$\left(\mathrm{Mg}\right)$ reacts most rapidly with Hydrochloric acid followed by Aluminium $\left(\mathrm{Al}\right)$, Zinc $\left(\mathrm{Zn}\right)$ and Iron $\left(\mathrm{Fe}\right)$.
• Magnesium reacts with Hydrochloric acid to form Magnesium chloride $\left({\mathrm{MgCl}}_2\right)$ and Hydrogen molecule.

$\mathrm{Mg}\left(\mathrm{s}\right)+2\mathrm{HCl}\left(\mathrm{aq}\right)\to {\mathrm{MgCl}}_2\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)$

• Aluminium reacts with Hydrochloric acid to form Aluminium chloride $\left({\mathrm{AlCl}}_3\right)$ and Hydrogen molecule.

$2\mathrm{Al}\left(\mathrm{s}\right)+6\mathrm{HCl}\left(\mathrm{aq}\right)\to 2{\mathrm{AlCl}}_3\left(\mathrm{aq}\right)+3{\mathrm{H}}_2\left(\mathrm{g}\right)$

• Zinc reacts with Hydrochloric acid to form Zinc chloride $\left({\mathrm{ZnCl}}_2\right)$ and Hydrogen molecule.

$\mathrm{Zn}\left(\mathrm{s}\right)+2\mathrm{HCl}\left(\mathrm{aq}\right)\to {\mathrm{ZnCl}}_2\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)$

• Iron reacts with Hydrochloric acid to form Iron(II) chloride $\left({\mathrm{FeCl}}_2\right)$ and Hydrogen molecule.

$\mathrm{Fe}\left(\mathrm{s}\right)+2\mathrm{HCl}\left(\mathrm{aq}\right)\to {\mathrm{FeCl}}_2\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)$

Final Answer: Hence, option A is correct. Correct Order is $\mathrm{Mg}>\mathrm{Al}>\mathrm{Zn}>\mathrm{Fe}$.