A reactant solution that has a molarity of 1.50 M needs to be diluted to
create a product with both a volume of 75.0 mL and 0.250 M. What
volume of the 1.50 M solution should be used to make this dilution?
(Hint: M1V1=M2V2)
0.00 5L
1.12
0.0125L
3.40L

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