Nitrogen has an atomic mass of 14.007 amu. Nitrogen has two common isotopes. One of the isotopes has a mass of 14.003 amu and a relative abundance of 99.632%. What is the % abundance of the other isotope?
What is the mass of the other isotope?

the answer is 75.0%.

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