Balance the half equation for this reaction to work out how many moles of electrons are needed to reduce one mole of nitrobenzene C6H5NO2+..........e- + ..........H+ = C6H5NH2+ .......H20?

1 Answer
Ernest Z.
Mar 24, 2018

You need six moles of electrons to reduce one mole of nitrobenzene.

Explanation:

You can find the general technique for balancing redox equations in acid solution here.

Step 1: Write the skeleton half-reaction.

#"C"_6"H"_5"NO"_2 → "C"_6"H"_5"NH"_2#

Step 2: Balance all atoms other than #"H"# and #"O"#.

Done.

Step 3: Balance #"O"#.

#"C"_6"H"_5"NO"_2 → "C"_6"H"_5"NH"_2 + "2H"_2"O"#

Step 4: Balance #"H"#.

#"C"_6"H"_5"NO"_2 + "6H"^"+" → "C"_6"H"_5"NH"_2 + "2H"_2"O"#

Step 5: Balance charge.

#"C"_6"H"_5"NO"_2 + "6H"^"+" + "6e"^"-" → "C"_6"H"_5"NH"_2 + "2H"_2"O"#

Step 6: Check mass balance.

#ulbb("Atom"color(white)(m)"On the left"color(white)(m)"On the right")#
#color(white)(ml)"C"color(white)(mmmmml)6color(white)(mmmmmmll)6#
#color(white)(ml)"H"color(white)(mmmmll)11color(white)(mmmmmml)11#
#color(white)(ml)"N"color(white)(mmmmml)1color(white)(mmmmmmll)1#
#color(white)(ml)"O"color(white)(mmmmml)2color(white)(mmmmmmll)2#

Step 9: Check charge balance.

#mathbf("On the left"color(white)(m)"On the right")#
#color(white)(mmm)0color(white)(mmmmmmll)0#

∴ The balanced half-reaction is

#"C"_6"H"_5"NO"_2 + "6H"^"+" + "6e"^"-" → "C"_6"H"_5"NH"_2 + "2H"_2"O"#

The reduction half-reaction involves six moles of electrons.

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