How do chemists predict the shapes of molecules? Chemists can't predict the shape of molecules, because the attractive forces between valence electrons are unpredictable.

Due to the repulsion between electrons, valence electrons will be arranged as close to each other as possible.

Due to the attraction between electrons, valence electrons will be arranged as close to each other as possible.

Due to the repulsion between electrons, valence electrons will be arranged as far apart from each other as possible.

the earth would become to overheated and everything alive on it will eventually die from overheating. plants will eventually die as well, water will evaporate, and it will be nothing but a hot planet without anything living on it.

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