Please help need asap so i can pass

Explanation:

83.0g        excess      ? mol

2Na    +    Cl2X    =  2 NaCl

2 mol       1 mol          2 mol

23g/mol

83g  x 1 mol/23g = 3.61 mol Na

3.61 mol Na X 2 mol NaCl/2 Mol Na  =3.6 mol NaCl

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