Which of the following metals reacts with steam but not with cold water?
A. Potassium
B. Magnesium
C. Calcium
D. Sodium
Answer: Option B
Solution (By JKSSB Mock Tests)
Magnesium reacts with hot water or steam to form MgO/Mg(OH)₂ and H₂, but very slowly with cold water (thin layer of insoluble hydroxide inhibits reaction). Sodium, potassium, and calcium react vigorously with cold water. Aluminium, zinc, iron react with steam but not cold water. Reactivity with water follows the series: K, Na, Ca (cold water); Mg, Al, Zn, Fe (steam).
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