Answer
Verified
327k+ views
Hint: Find a reagent which gives precipitate with either formic acid or acetic acid but not with both. Recall that the formic acid carbonyl bond is also connected to a hydrogen atom.
Complete step by step answer:
One way to distinguish between formic acid and acetic acid is Tollen’s test. This test is also known as the silver mirror test. Formic acid gives Tollens test whereas acetic acid does not give this test. Tollen’s reagent is an ammoniacal silver nitrate solution. When formic acid is heated with Tollen’s reagent, a silver mirror is formed on the inner sides of the test tube. Acetic acid does not give this test.
Write the chemical reaction for the silver mirror test.
\[\begin{array}{l}
{\rm{HCOOH + 2 }}{\left[ {{\rm{Ag}}{{\left( {{\rm{N}}{{\rm{H}}_3}} \right)}_2}} \right]^ + }{\rm{ + 2O}}{{\rm{H}}^ - } \to {\rm{ }}2{\rm{Ag}} \downarrow {\rm{ }} + {\rm{ C}}{{\rm{O}}_2} + {\rm{ 2}}{{\rm{H}}_2}{\rm{O + 4N}}{{\rm{H}}_3}\\
{\rm{Formic acid Tollen's reagent Silver mirror}}\\
{\rm{C}}{{\rm{H}}_3}{\rm{COOH + 2 }}{\left[ {{\rm{Ag}}{{\left( {{\rm{N}}{{\rm{H}}_3}} \right)}_2}} \right]^ + }{\rm{ + 2O}}{{\rm{H}}^ - } \to {\rm{ Silver mirror is NOT formed}}
\end{array}\]
Tollen’s test is also given by aldehydes.
Formic acid and acetic acid can also be distinguished by \[{\rm{HgC}}{{\rm{l}}_2}\] test. Formic acid forms a white precipitate with \[{\rm{HgC}}{{\rm{l}}_2}\] whereas acetic acid does not form any precipitate with \[{\rm{HgC}}{{\rm{l}}_2}\].
\[\begin{array}{l}
{\rm{HCOOH + 2 HgC}}{{\rm{l}}_2} \to {\rm{ H}}{{\rm{g}}_2}{\rm{C}}{{\rm{l}}_2} \downarrow {\rm{ }} + {\rm{ C}}{{\rm{O}}_2} + {\rm{ 2HCl}}\\
{\rm{Formic acid Mercuric Mercurous}}\\
{\rm{ chloride chloride}}\\
{\rm{ }}\left( {{\rm{white ppt}}} \right){\rm{ }}\\
{\rm{C}}{{\rm{H}}_3}{\rm{COOH + 2 HgC}}{{\rm{l}}_2} \to {\rm{ No precipitate obtained}}
\end{array}\]
Note:
Please do not use the iodoform test which is characteristic of methyl ketones. In the Iodoform Test, we obtain a yellow precipitate in case of methyl ketones. This will not work in this situation.
Complete step by step answer:
One way to distinguish between formic acid and acetic acid is Tollen’s test. This test is also known as the silver mirror test. Formic acid gives Tollens test whereas acetic acid does not give this test. Tollen’s reagent is an ammoniacal silver nitrate solution. When formic acid is heated with Tollen’s reagent, a silver mirror is formed on the inner sides of the test tube. Acetic acid does not give this test.
Write the chemical reaction for the silver mirror test.
\[\begin{array}{l}
{\rm{HCOOH + 2 }}{\left[ {{\rm{Ag}}{{\left( {{\rm{N}}{{\rm{H}}_3}} \right)}_2}} \right]^ + }{\rm{ + 2O}}{{\rm{H}}^ - } \to {\rm{ }}2{\rm{Ag}} \downarrow {\rm{ }} + {\rm{ C}}{{\rm{O}}_2} + {\rm{ 2}}{{\rm{H}}_2}{\rm{O + 4N}}{{\rm{H}}_3}\\
{\rm{Formic acid Tollen's reagent Silver mirror}}\\
{\rm{C}}{{\rm{H}}_3}{\rm{COOH + 2 }}{\left[ {{\rm{Ag}}{{\left( {{\rm{N}}{{\rm{H}}_3}} \right)}_2}} \right]^ + }{\rm{ + 2O}}{{\rm{H}}^ - } \to {\rm{ Silver mirror is NOT formed}}
\end{array}\]
Tollen’s test is also given by aldehydes.
Formic acid and acetic acid can also be distinguished by \[{\rm{HgC}}{{\rm{l}}_2}\] test. Formic acid forms a white precipitate with \[{\rm{HgC}}{{\rm{l}}_2}\] whereas acetic acid does not form any precipitate with \[{\rm{HgC}}{{\rm{l}}_2}\].
\[\begin{array}{l}
{\rm{HCOOH + 2 HgC}}{{\rm{l}}_2} \to {\rm{ H}}{{\rm{g}}_2}{\rm{C}}{{\rm{l}}_2} \downarrow {\rm{ }} + {\rm{ C}}{{\rm{O}}_2} + {\rm{ 2HCl}}\\
{\rm{Formic acid Mercuric Mercurous}}\\
{\rm{ chloride chloride}}\\
{\rm{ }}\left( {{\rm{white ppt}}} \right){\rm{ }}\\
{\rm{C}}{{\rm{H}}_3}{\rm{COOH + 2 HgC}}{{\rm{l}}_2} \to {\rm{ No precipitate obtained}}
\end{array}\]
Note:
Please do not use the iodoform test which is characteristic of methyl ketones. In the Iodoform Test, we obtain a yellow precipitate in case of methyl ketones. This will not work in this situation.
Recently Updated Pages
silver wire has diameter 04mm and resistivity 16 times class 12 physics JEE_Main
A parallel plate capacitor has a capacitance C When class 12 physics JEE_Main
Let gx 1 + x x and fx left beginarray20c 1x 0 0x 0 class 12 maths JEE_Main
A series combination of n1 capacitors each of value class 12 physics JEE_Main
When propyne is treated with aqueous H2SO4 in presence class 12 chemistry JEE_Main
Which of the following is not true in the case of motion class 12 physics JEE_Main
Other Pages
The resultant of vec A and vec B is perpendicular to class 11 physics JEE_Main
when an object Is placed at a distance of 60 cm from class 12 physics JEE_Main
Differentiate between homogeneous and heterogeneous class 12 chemistry JEE_Main
Oxidation state of S in H2S2O8 is A 6 B 7 C +8 D 0 class 12 chemistry JEE_Main
If a wire of resistance R is stretched to double of class 12 physics JEE_Main
Dissolving 120g of urea molwt60 in 1000g of water gave class 11 chemistry JEE_Main