I just need some help on some Chem... 3. What is a chemical bond having a dipole? 4. What is a chemical bond that has NO dipole? 5. What is a chemical bond in which an attractive electric force holds ions of opposite charges together? 6. What is a chemical bond in which atoms are held together by their mutual attraction for two or more electrons they share? 7. What is a group of atoms of different elements held tightly together by covalent bonds?

the answer to your question is c

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