PTC gene has two main alleles; one that codes for tasting and the other non-tasting. The allele for tasting determines a trait of tongue papillae that can bind the PTC molecules. Non-tasting allele forms papillae that are unable to bind PTC effectively. Therefore, the combination of these alleles in the genotype of a person determines their phenotype – PTC sensitivity.

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

it's 3.2 on edge, i just took the test.