Suppose a new metallic element x is discovered, and its reactions with oxygen gas and chlorine gas at 298 k are studied. trial reaction δhºrxn (kj/mol) 1 4x(s) 3o2(g) → 2x2o3(s) –600 2 2x(s) 3cl2(g) → 2xcl3(s) –800 3 4xcl3(s) 3o2(g) → 2x2o3(s) 6cl2(g) –200 however, it is later discovered that one of the samples was contaminated, and the δhºrxn value from this trial is not reliable. which trial had the contaminated sample, and what should the correct value of δhºrxn be for this trial

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

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