Use the reaction below for the combustion of methanol. Any type of stoichiometry problem is possible.
2CH3OH(I) + 302(g) → 2C02(g) + 4H2O(1)
What mass of methanol is combusted in a reaction that produces 112
L of CO2 at STP?
a 64.13 CH3OH
b 81.6 g CH3OH
C 160. g CH3OH
d 112 g CH3OH

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