Question

Metal, which will displace hydrogen from dilute HCl is :

• A. Ag
• B. Au
• C. Mg
• D. Cu

Hint:

To displace hydrogen from dilute acids (like HCl), a metal must be {more reactive than hydrogen}. This means the metal must be {above hydrogen (H)} in the reactivity series. % Option (V) Mg: Above H (Yes, displaces) % Option (W) Ag, Au, Cu: Below H (No, do not displace)

Answer 1

The Correct Option is C

Concept: The ability of a metal to displace hydrogen from an acid (like dilute HCl) depends on its position in the reactivity series (also known as the activity series of metals). Metals above hydrogen in the reactivity series are more reactive than hydrogen and can displace it from dilute non-oxidizing acids. Step 1: Understanding the Reactivity Series The reactivity series arranges metals in order of their decreasing reactivity. A simplified portion relevant here is: K>Na>Ca>Mg>Al>Zn>Fe>Sn>Pb>(H)>Cu>Hg>Ag>Pt>Au (Highly reactive \(\rightarrow\) Least reactive) Metals {above} Hydrogen (H) in this series will displace hydrogen from dilute acids like HCl or \(H_2SO_4\). Metals {below} Hydrogen will not displace hydrogen from these acids. Step 2: Analyzing the options based on their position relative to Hydrogen % Option (R) (1) Ag (Silver): Silver is {below} hydrogen in the reactivity series. Therefore, it cannot displace hydrogen from dilute HCl. (Reaction: \(Ag + HCl \rightarrow \text{No reaction}\)) % Option (S) (2) Au (Gold): Gold is far {below} hydrogen in the reactivity series (it's a very unreactive noble metal). It cannot displace hydrogen from dilute HCl. (Reaction: \(Au + HCl \rightarrow \text{No reaction}\)) % Option (T) (3) Mg (Magnesium): Magnesium is well {above} hydrogen in the reactivity series. Therefore, it is more reactive than hydrogen and will displace it from dilute HCl. Reaction: \(Mg(s) + 2HCl(aq) \rightarrow MgCl_2(aq) + H_2(g)\) % Option (U) (4) Cu (Copper): Copper is {below} hydrogen in the reactivity series. Therefore, it cannot displace hydrogen from dilute HCl. (Reaction: \(Cu + HCl \rightarrow \text{No reaction}\)) Step 3: Identifying the correct metal Magnesium (Mg) is the only metal among the options that is more reactive than hydrogen and thus will displace hydrogen from dilute HCl.