Metallurgy, Metals, Non-Metals & Alloy RRB PYQ

The reactivity series of metals determines which metal can displace another metal from its salt solution. A more reactive metal displaces a less reactive one from its solution. From the given conditions: A can displace B → A is more reactive than B. B can displace D → B is more reactive than D. C can displace D → C is more reactive than D. C can displace A → C is more reactive than A. Since C can displace A, and A can already displace B and D, it means C is the most reactive metal in the given set.

Calcium reacts less vigorously than sodium but more than magnesium, forming calcium hydroxide and hydrogen gas: Ca + 2H2O → Ca(OH)2 + H2. Calcium is positioned below sodium but above magnesium in the reactivity series; consequently, its reaction with cold water is steady and manageable compared to the violent, explosive reaction of sodium. During the reaction, the calcium metal often starts to float because the bubbles of hydrogen gas produced stick to the surface of the metal pieces.