JEE Main 2022 · Chemistry · Mole Concept and Stoichiometry · medium

10 mL of a gaseous hydrocarbon CxHy is exploded with 80 mL of O2. After cooling to the initial conditions (water condensed) the volume is 65 mL, and…

Numerical answer

10\ \mathrm{mL}

of a gaseous hydrocarbon

\mathrm{C_xH_y}

is exploded with

80\ \mathrm{mL}

\mathrm{O_2}

. After cooling to the initial conditions (water condensed) the volume is

65\ \mathrm{mL}

, and it decreases to

35\ \mathrm{mL}

on passing through aqueous KOH. The value of

x+y

Show answer and solution

Answer: 9

KOH absorbs

\mathrm{CO_2}

: volume

=65-35=30\ \mathrm{mL}

, and

10\ \mathrm{mL}

of hydrocarbon gives

30\ \mathrm{mL}

, so

x=3

. The remaining

35\ \mathrm{mL}

is unused

\mathrm{O_2}

, so

\mathrm{O_2}

consumed

=80-35=45\ \mathrm{mL}

, i.e.

4.5

volumes per volume of hydrocarbon. From

\mathrm{C_xH_y+(x+y/4)O_2\to xCO_2+(y/2)H_2O(l)}

x+y/4=4.5\Rightarrow y=6

. The gas is propene,

x+y=9

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