One of the problems with using hydrogen gas as a fuel to power cars is that it must be stored in high pressure tanks. The high pressure tanks that would be required to take a car a reasonable distances between refuelling stops are often far too large for the average vehicle. What would be the necessary internal volume of a tank that stored hydrogen at 20.0 atm, if you needed to store enough hydrogen to react with 1435 g of oxygen gas at 32oC according to the chemical equation below? 2 H2(g) + O2(g) H2O(g)

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