What gas is released when acid added to a metal?

1 Answer
Truong-Son N.
May 10, 2017

Depends on what acid and what metal...

Two acids that are often reacted with metals are #"HNO"_3# and #"HCl"#. The former follows the #bb("NO"_3^(-))# reduction

#"NO"_3^(-)(aq) + 4"H"^(+)(aq) + 3e^(-) -> "NO"(g) + 2"H"_2"O"(l)#

and the latter from the Standard Hydrogen Electrode

#2"H"^(+)(aq) + 2e^(-) -> "H"_2(g)#.

If and only if a reaction occurs, then either #"H"_2(g)# is released from reaction with #"HCl"(aq)#, or #"NO"(g)# is released from reaction with #"HNO"_3(aq)#.

But you must decide which acid you refer to...

CHALLENGE: Which of the following is dissolved by #"HNO"_3# but not #"HCl"#?

  • #"Au"#
  • #"Ag"#
  • #"Fe"#
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