At STP, fluorine is a gas and bromine is a liquid because, compared to fluorine, bromine has 1.
stronger covalent bonds
2.
stronger intermolecular forces
3.
weaker covalent bonds
4.
weaker intermolecular forces

? you expect us to answer this? ? this is your schoolwork, i don't think we can with this, i think it would considering being

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