Which one of the following elements can not displace hydrogen gas from a dilute acid?

The ability of a metal to displace hydrogen gas from a dilute acid depends on its position in the reactivity (activity) series relative to hydrogen. Metals located above hydrogen in the series are more reactive and can displace hydrogen from acids to form a salt and hydrogen gas [2]. Magnesium, zinc, and iron are all positioned above hydrogen in the reactivity series, meaning they react with dilute hydrochloric acid to produce bubbles of hydrogen gas [1]. In contrast, copper is less reactive than hydrogen and is positioned below it in the electrochemical series [t2][t4]. Consequently, copper does not react with dilute acids like HCl or H2SO4 to displace hydrogen [1][t5]. This lack of reaction is evidenced by the absence of bubbles or temperature changes when copper is placed in dilute acid [1]. Therefore, among the given options, copper is the element that cannot displace hydrogen gas.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > Activity 3.11 > p. 44
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 2: Acids, Bases and Salts > Activity 2.3 > p. 20