What are the constituent ions in the ionic compound fecr2o7
a: 1fe+ cation and 1 cr2o7-
b: 1fe2+ cation and 1 cr2o7-
c 1fe2+ cation 2 cr6+cations and 7 o2- anions
s
d 1 fecr2 14 cation 7 o2- anions

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