Calculate the enthalpy change for the following reaction: N2H4(g)+O2(g)→N2(g)+2H2O(l), ΔHrxn∘=? Given the following enthalpies of formation: N2(g)+2H2(g)→N2H4(g), ΔH1=95.4kJ H2(g)+1/2O2(g)→H2O(l), ΔH2=−285.8kJ

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

answersilicon (si); oxygen (o);