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InterviewSolution
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A gas mixture of `4` litres of ethylene and methane on complete combustion at `25^(@)C` produces `6` litres of `CO_(2)`. Find out the amount of heat evolved on burning one litre of the gas mixture. The heats of combustion of ethylene and methane are`-1464` and `-976 KJ mol^(-1)` at `25^(@)C` |
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Answer» gt `X "moles"" " (4-x)"moles" " "6"moles"` Applying `POAC` for `C` atoms, `2xxx+1xx(4-x)=1xx6, x=2 "lit"` Thus, the volume of ` C_(2)H_(4)=2"lit"`, and volume of `CH_(2)=2"lit"`. `:.` volume of `C_(2)H_(4)` in a `1` litre mixture `=2//4=0.5 "lit"`. and volume of `CH_(4)` in a `1` litre mixture `=1-0.5=0.5"lit"` Now, thermochemical reactions for `C_(2)H_(4)` and `CH_(4)` are `{:(C_(2)H_(4)+3O_(2)rarr2CO_(2)+2H_(2)O, Delta H= -1464KJ,,,,),(CH_(4)+2O_(2)rarrCO_(2)+2H_(2)O, Delta H= -976 KJ,,,,):}` As `Delta H` values given at `25^(@)C`. let us first calculate the volume occupied by one mole of any gas at `25^(@)C` (supposiong pressures as `1 atm`) Volume per mole at `25^(@)C=(298)/(273)xx22.4=24.4"lit"` Thus, heat evolved in the combustion of `0.5` lit of `C_(2)H_(4)=(1464)/(24.4)xx0.5= -30KJ` and heat evolved in the combustion of `0.5` lit of `CH_(4)=(976)/(24.4)xx0.5=-20KJ`. `:.` total heat evolved in the combustion of `1` litre of the mixture `= -30+(-20)= -50 KJ` |
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