What kind of chemical/gas/radiation that is invisible can be sprayed by some kind of mechanism making anything that it gets on spoil, change smell of things making it smell stronger & pugnet, or when it hits human body or anything ingested that this chemical/gas/radiation got sprayed or on somehow that would make your heart beat heavy & fast?

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

answerambulatory;