A student performed a recrystallization and after the solid dissolved, the solution was immediately placed in an ice bath. Within a few seconds, a large amount of solid formed and was collected by vacuum filtration. The percent recovery was high but the melting point of the dried solid showed that the solid was contaminated with impurities. Could you explain very specifically why it happened?

it is a good conductor

explanation:

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