question_answer

How will you separate a mixture of ethane, ethylene and acetylene?

Answer:

                This mixture can be separated into its constituents by the following steps: Step 1. Pass the mixture of gases through Tollens' reagent when acetylene will form white precipitate of disilver acetylide while ethane and ethylene will pass through. \[\underset{Acetylene}{\mathop{HC\equiv CH}}\,+\underset{Tollens'\,reagent}{\mathop{2\,{{[Ag{{(N{{H}_{3}})}_{2}}]}^{+}}O{{H}^{-}}}}\,\xrightarrow{{}}\underset{Disilver\,acetylide}{\mathop{Ag-C\equiv C-Ag}}\,+4\,N{{H}_{3}}+2\,{{H}_{2}}O\]                Separate the white ppt. by filtration and treat it with dil. \[HN{{O}_{3}}\] to regenerate acetylene. Collect it in a separate container. \[Ag-C\equiv C-Ag+2\,HN{{O}_{3}}\xrightarrow{{}}HC\equiv CH+2\,AgN{{O}_{3}}\] Step 2. Pass the remaining mixture of ethane and ethylene through cold conc. \[{{H}_{2}}S{{O}_{4}}\]when ethylene will be absorbed as ethyl hydrogen sulphate while ethane escapes. The ethane thus obtained is collected in a separate container. \[\underset{\text{Ethylene}}{\mathop{C{{H}_{2}}=C{{H}_{2}}}}\,+{{H}_{2}}S{{O}_{4}}\,(conc.)\xrightarrow{\,}\]\[\underset{\text{Ethyl}\,\,\text{hydrogen}\,\text{sulphate}}{\mathop{C{{H}_{3}}C{{H}_{2}}OS{{O}_{2}}OH}}\,\] The ethyl hydrogen sulphate thus obtained is heated with conc. \[{{H}_{2}}S{{O}_{4}}\] to 433 - 443 K when ethylene is obtained which is collected in a separate container \[C{{H}_{3}}C{{H}_{2}}OS{{O}_{3}}H\xrightarrow{433-443K}\,C{{H}_{2}}=C{{H}_{2}}+{{H}_{2}}S{{O}_{4}}\]