What are the respective concentrations (M) of Cu+2 and Cl' afforded by dissolving 0.200 mol CuCl2 in water and diluting to 345 mL?
A) 0.200 and 0.200
B) 0.580 and 1.16
C 0.200 and 0.400
D) 1.16 and 2.32
E 0.580 and 0.290

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