Compare: The mass number of C-12 is 12, a value representing the total number of protons and neutrons in the nucleus. Since both protons and neutrons have masses that are just over 1 u, the mass number will typically be very close to the atom’s mass. Add a few atoms each of C-12 and C-13 to the chamber, press Release atoms, and then click on the bars of the graph to reveal a close-up image of each isotope. 1. How does the proton number in each isotope compare?
2. How does the neutron number in each compare?
3. What can you conclude about the role of neutrons in forming new isotopes?

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

answerambulatory;