Which process requires energy to decompose a
substance?

electrolysis

Explanation:

Electrolysis is one process that requires energy to decompose a substance into another one.

Electrolysis is a chemical process which converts electrical energy into chemical energy.

This process actually involves the decomposition of ionic compounds when electric current is passed through into an aqueous solution or molten form of the compound via the electrodes.

they are all solids.

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