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Which of the following metals cannot displace hydrogen from cold water ?A. `K`B. `Mg`C. `Ca`D. `Na`

Answer» Correct Answer - B
All alkali metals and some alkaline earth metals (Ca,Sr, and Ba) which are the most reactive of the metallic elements will displace hydrogen from cold water :
`Ca(s) + 2 H_2O(1) rarr Ca (OH)_2(s) + H_2(g)`
`Mg(s) + 2H_2O(1) rarr` No reaction
Mg reacts with ` H_2O` only at higher temperature.


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