What condition must occur when a chemical reaction is at equilibrium?

Explanation:

The conditions that must occur when a chemical reaction is at equilibrium are as follows -

At equilibrium there is no net change in the amounts of reacting species and product forming species and the concentration of the reactants and products are constant.

A reaction is is said to be in chemical equilibrium if the rate of the forward reaction and the rate of the backward reaction is equal.

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