Hydrazine can be used as a rocket fuel. A 6.4 g sample of hydrazine is found to contain 5.6 g of nitrogen and 0.80 g of hydrogen. The molar mass of hydrazine is
the same as that of oxygen gas. Determine the empirical formula and the
molecular formula of this compound. (show work; use labels)

it is b that is the answer.

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