Someone please help: 5.2cm^3 of gaseous hydrocarbon were exploded in excess oxygen. After cooling to the original room temperature and pressure a contraction in volume of 15.6cm^3 was observed. A further contraction of 10.4cm^3 was noted after treatment with concentrated KOH. What is the molecular formula for the hydrocarbon?

answer : third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol

explanation :

let us write down the given equations

equation 1 :

equation 2 :

equation 3 :

let us use hess's law to find out which 2 equations can be added to get the third equation.

let us reverse equation 2 and multiply it by 2. the new equation that we get is,

equation 4 :

let us add equation 1 & 4

the above equation is similar to equation 3 but has different value for dhrxn.

therefore third trial had the contaminated sample and the correct value for dhrxn should be 1000 kj/mol