50 mL of a gaseous hydrocarbon is mixed with excess of oxygen and burnt and cooled to thelaboratory temperature. Thereduction in volume wasfound to be150 mL. The gas is then passed intocaustic potash, when there is a further reduction inthe volume of 150 mL. Provide all thevolumesare measured at the same conditions of temperature and pressure, find out themolecular formula of thehydrocarbon.

50 mL of a gaseous hydrocarbon is mixed with excess of oxygen and burn

1.	50 mL of a gaseous hydrocarbon is mixed with excess of oxygen and burnt and cooled to thelaboratory temperature. Thereduction in volume wasfound to be150 mL. The gas is then passed intocaustic potash, when there is a further reduction inthe volume of 150 mL. Provide all thevolumesare measured at the same conditions of temperature and pressure, find out themolecular formula of thehydrocarbon.
Answer» Solution :Chemical REACTION equation to combustion reaction is `{:(C_(x)H_(y)+O_(2) to CO_(2)+H_(2)O),("50ML"" 150mL""150mL"):}` We know volume of gas has same number of moles, at same temperature andpressure `{:("50 moles"" 150 moles""150 moles"),(C_(x)H_(y)+(x+y/4)O_(2) toxCO_(2) + y/2 H_(2)O),("50 MOLE""150 mole""150 mole"):}` Given that reduction in volume, when thegases mixture is cooled to the laboratory temperature = 150 ML `:. y/2 (50) = 150 rArr y = 6`. and `x (50) = 150 rArr x = 3` `:.` Hydrocarbon is `C_(3)H_(6)`.