Verified Solution • 2025–26 Session moderate

QJEEAdv17Chd08b: JEE Advanced 2017 Chemistry - Class 12 JEEAdv17Chd08b Solution: Which of the following combination will produce gas ?

Which of the following combination will produce H2{H_2} gas ?

Multiple Choice Options

  • A CuCu metal and conc. HNO3HN{O_3}
  • B ZnZn metal and NaOH(aq)NaOH(aq)
  • C Au metal and NaCN(aq)NaCN\left( {aq} \right) in the presence of air
  • D Fe metal and conc. HNO3HN{O_3}

Step-by-Step Verified Solution

(a) Conc. HNO3 makes iron passive. Cold relatively concentrated HNO3 will react with Fe.

FeIron+6HNO3Nitric acid→Fe(NO3)3Iron nitrate+3NO2Nitrogen dioxide+3H2OWater\mathop {Fe}\limits_{Iron} + \mathop {6HN{O_3}}\limits_{Nitric\,acid} \to \mathop {Fe{{(N{O_3})}_3}}\limits_{Iron\,nitrate} + \mathop {3N{O_2}}\limits_{Nitrogen\,dioxide} + \mathop {3{H_2}O}\limits_{Water}

(b) CuCopper+4HNO3(conc.)Nitric acid→Cu(NO3)2Copper nitrate+2NO2Nitrogen dioxide+2H2OWater\mathop {Cu}\limits_{Copper} + \mathop {4HN{O_3}(conc.)}\limits_{Nitric\,acid} \to \mathop {Cu{{(N{O_3})}_2}}\limits_{Copper\,nitrate} + \mathop {2N{O_2}}\limits_{Nitrogen\,dioxide} + \mathop {2{H_2}O}\limits_{Water}

(c) ZnZinc+2NaOH(aq)Sodium hydroxide→Na2ZnO2Sodium zincate+H2Hydrogen\mathop {Zn}\limits_{Zinc} + \mathop {2NaO{H_{(aq)}}}\limits_{Sodium\,hydroxide} \to \mathop {N{a_2}Zn{O_2}}\limits_{Sodium\,zincate} + \mathop {{H_2}}\limits_{Hydrogen}

(d) 4AuGold+8NaCNSodium cyanide+O2Oxygen+2H2OWater→4Na[Au(CN)2]Sodium dicyanoaurate+4NaOHSodium hydroxide\mathop {4Au}\limits_{Gold} + \mathop {8NaCN}\limits_{Sodium\,cyanide} + \mathop {{O_2}}\limits_{Oxygen} + \mathop {2{H_2}O}\limits_{Water} \to \mathop {4Na[Au{{(CN)}_2}]}\limits_{Sodium\,dicyanoaurate} + \mathop {4NaOH}\limits_{Sodium\,hydroxide}

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