If a material absorbs a certain frequency of visible light, that frequency
A.
will not be reflected, so its color will be perceived by an observer.
B.
will not be reflected, so its color will not be perceived by an observer.
C.
will be reflected, so its color will be perceived by an observer.
D.
will be reflected, so its color will not be perceived by an observer.

idk

explanation:

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