A) Copper and cone. nitric acid
B) Ethanol and metallic sodium
C) Magnesium and steam
D) Phenol and metallic sodium
E) Sodium hydride and water
Correct Answer: D
Solution :
Copper, being less reactive, when reacts with cone. nitric acid, gives\[N{{O}_{2}},\]but not\[{{H}_{2}}\]. \[Cu+4HN{{O}_{3}}(conc)\xrightarrow{{}}Cu{{(N{{O}_{3}})}_{2}}\] \[+2N{{O}_{2}}+2{{H}_{2}}O\] while\[Mg\]and\[NaH\]being very reactive give hydrogen gas with steam and water respectively. \[Mg+2{{H}_{2}}O\xrightarrow{{}}MgO+{{H}_{2}}\] \[NaH+{{H}_{2}}O\xrightarrow{{}}NaOH+{{H}_{2}}\] Ethanol and phenol due to the presence of acidic hydrogen also produce hydrogen with metallic sodium. \[{{C}_{2}}{{H}_{5}}OH+Na\xrightarrow{{}}{{C}_{2}}{{H}_{5}}{{O}^{-}}N{{a}^{+}}+{{H}_{2}}\] \[{{C}_{6}}{{H}_{5}}OH+Na\xrightarrow{{}}{{C}_{6}}{{H}_{5}}{{O}^{-}}N{{a}^{+}}+{{H}_{2}}\]
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