2.A plant's leaves are green because the color green is back to our eyes. * O A. Absorbed
OB. Reflected
O C. Transmitted
O D. All of the above​

"record the time to complete a chemical reaction" would most likely be part of a lab procedure.

i think its 5049.

i hope this !

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