What is the equation for the reaction with Butan-1-ol with [o] acidified ##K_2Cr_2O_7##?

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February 20th, 2023

The butan-1-ol is oxidized to butanoic acid, and the dichromate ion is reduced to chromium(III) ion.
The method of balancing redox equations is described ,
1: Separate into two half-reactions.
##”CH”_3″CH”_2″CH”_2″CH”_2″OH” → “CH”_3″CH”_2″CH”_2″COOH”##
##”Cr”_2″O”_7^”2-” → “Cr”^”3+”##
2: Balance all atoms other than H and O.
##”CH”_3″CH”_2″CH”_2″CH”_2″OH” → “CH”_3″CH”_2″CH”_2″COOH”##
##”Cr”_2″O”_7^”2-” → color(red)(2)”Cr”^”3+”##
3: Balance ##”O”##
##”CH”_3″CH”_2″CH”_2″CH”_2″OH” + “H”_2″O” → “CH”_3″CH”_2″CH”_2″COOH”##
##”Cr”_2″O”_7^”2-” → color(red)(2)”Cr”^”3+”+ color(blue)(7)”H”_2″O”##
4: Balance H.
##”CH”_3″CH”_2″CH”_2″CH”_2″OH” + “H”_2″O” → “CH”_3″CH”_2″CH”_2″COOH” + color(brown)(4)”H”^+##
##”Cr”_2″O”_7^”2-” + color(brown)(14)”H”^+ → color(red)(2)”Cr”^”3+”+ color(blue)(7)”H”_2″O”##
5: Balance charge.
##”CH”_3″CH”_2″CH”_2″CH”_2″OH” + “H”_2″O” → “CH”_3″CH”_2″CH”_2″COOH” + color(brown)(4)”H”^+ + color(magenta)(4)e^”-“##
##”Cr”_2″O”_7^”2-” + color(brown)(14)”H”^+ + color(magenta)(6)e^”-” → color(red)(2)”Cr”^”3+”+ color(blue)(7)”H”_2″O”##
6: Equalize electrons transferred.
##3 × [“CH”_3″CH”_2″CH”_2″CH”_2″OH” + “H”_2″O” → “CH”_3″CH”_2″CH”_2″COOH” + color(brown)(4)”H”^+ + color(magenta)(4)e^”-“]##
##2 × [“Cr”_2″O”_7^”2-” + color(brown)(14)”H”^+ + color(magenta)(6)e^”-” → color(red)(2)”Cr”^”3+”+ color(blue)(7)”H”_2″O”]##
7: Add the two half-reactions.
##3″CH”_3″CH”_2″CH”_2″CH”_2″OH” + 2″Cr”_2″O”_7^”2-” + color(brown)(16)”H”^+ → 3″CH”_3″CH”_2″CH”_2″COOH” + color(red)(4)”Cr”^”3+”+ color(blue)(11)”H”_2″O”##
8: Check mass balance.
##”Atom”color(white)(m)”On the left”color(white)(m)”On the right”##
##color(white)(m)”C”color(white)(mmmm)12color(white)(mmmmml)12##
##color(white)(m)”H”color(white)(mmmm)46color(white)(mmmmml)46##
##color(white)(m)”O”color(white)(mmmm)17color(white)(mmmmml)17##
##color(white)(m)”Cr”color(white)(mmmml)4color(white)(mmmmmll)4##
9: Check charge balance.
##color(white)(mm)”On the left”color(white)(mm)”On the right”##
##color(white)(m)”4- + 16+ = 12+”color(white)(mml)”12+”##
The balanced equation is
##3″CH”_3″CH”_2″CH”_2″CH”_2″OH” + 2underbrace(color(orange)(“Cr”_2″O”_7^”2-“))_color(orange)(“orange”) + 16″H”^+ → 3″CH”_3″CH”_2″CH”_2″COOH” + 4underbrace(color(green)(“Cr”^”3+”))_color(green)(“green”) + 11″H”_2″O”##
The ##color(orange)(“orange dichromate ion”## is converted to the ##color(green)(“green chromium(III) ion”)##.