devarshi-dt-logo

Question:

Which of the following combinations will produce H2 gas?

Au metal and NaCN(aq) in the presence of air

Zn metal and NaOH(aq)

Cu metal and conc. HNO3

Fe metal and conc. HNO3

Solution:

Zn metal and NaOH(aq) will produce hydrogen gas. Zn + 2NaOH → Na₂ZnO₂ + H₂↑