The graph represents the amount of energy in the reactants and products of a chemical reaction.
If total energy is conserved, which statement
explains why the energy of the reactants does not
equal the energy of the products?
Energy
Energy of Energy of
Reactants Products
A.
The reaction is exothermic
B. The reaction is endothermic.
C. The reaction requires a catalyst.
D
The reaction has a low activation energy.

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