In the picture, the different shapes (circle, triangle, and a square) represent different elements. Which of the following represents a pure substance?
A) Figure W&X
B)Figure W&Y
C) figure Z&Y
D) figure Z&W

increased stability in the completion of fluorine's outer shell.

i'm wiling to try and you : )

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

the answers are

c and c